Intermittent Conditions
| Inspections | Action |
|---|
| DEFINITION: The condition is not currently present but is indicated in DTC history. OR There is a customer concern, but the symptom cannot currently be duplicated, if the condition is not DTC related. |
| Preliminary | Refer to Important Preliminary Inspection Before Starting in Symptoms - Engine Controls . The fault must be present to locate a problem using the DTC table. If a fault is intermittent, the use of DTC tables may result in the replacement of good parts. |
| Visual/Physical | This step is an important aid for locating a condition without extensive testing. Perform a thorough visual and physical inspection of the following components: Wiring harness for damage or cuts A misrouted harness that is too close to high voltage or high current devices such as the following: Secondary ignition components Motors Generators Vacuum hoses for the following conditions: Proper routing Proper connections Splits in the hose or the connections Kinks Air leaks at the throttle body mounting area - Refer to Throttle Body Service . Air leaks at the mass air flow (MAF) sensor and at the intake manifold Engine control module (ECM) and body grounds are clean and tight Battery connections are clean and tight Charging system for proper operation - Refer to Charging System Test in Engine Electrical. |
| Harness/Connector Test | Many intermittent open or shorted circuits come and go with harness and connector movement caused by vibration, engine torque, bumps and rough pavement, etc. Test for this type of condition by performing the applicable procedure from the following list: Move the related connectors and wiring while monitoring the appropriate scan tool data. Move the related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the components operation. With the engine running, move the related connectors and wiring while monitoring engine operation. If harness or connector movement affects the data displayed, the component and system operation, or the engine operation, inspect and repair the harness or connections as necessary. Refer to Electrical Connections or Wiring in this table. |
| Electrical Connections or Wiring | Poor electrical connections and terminal tension or wiring faults cause most intermittents. Perform a careful inspection of the suspected circuit for the following: Inspect for incorrect mating of the connector halves, or terminals not fully seated in the connector body, backed-out. Inspect for improperly formed or damaged terminals. Test for incorrect terminal tension. Inspect for poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body. Inspect for corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits. Inspect for wires that are broken inside the insulation. Inspect the harness for pinched, cut, or rubbed through wiring. Make sure the wiring does not come in contact with hot exhaust components. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. |
| ECM Power and Grounds | Poor power or ground connections can cause widely varying symptoms. Test all engine control module (ECM) power circuits. Many vehicles have multiple circuits supplying power to the ECM. Inspect connections at the ECM connectors, fuses, and any intermediate connections between the power source and the ECM or component. A test lamp or a DMM may indicate that voltage is present, but neither tests a circuits ability to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. Refer to Power Distribution Schematics in Wiring Systems. Test all ECM ground and system ground circuits. The ECM may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Make sure the ground connections are clean and tight at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. |
| Temperature Sensitivity | An intermittent condition may occur only when the component is cold, or only when the component is hot. The heat that affects the circuit can be engine generated or due to a poor connection in the circuit or a high electrical load. Information from the customer may help to determine if the trouble follows a pattern that is temperature related. The Freeze Frame/Failure Records or Snapshot data may help with this type of intermittent condition, where applicable. If the intermittent is related to heat, review the data for a relationship with the following: High ambient temperatures Underhood/engine generated heat Circuit generated heat due to a poor connection, or high electrical load Higher than normal load conditions (towing, etc.) If the intermittent is related to cold, review the data for the following: Low ambient temperatures-In extremely low temperatures, ice may form in a connection or component. Inspect for water intrusion. The condition only occurs on a cold start. The condition goes away when the vehicle warms up. |
| Electromagnetic Interference (EMI) and Electrical Noise. | Some electrical components and circuits are sensitive to electromagnetic interference (EMI) or other types of electrical noise. Inspect for the following conditions: A misrouted harness that is too close to high voltage and high current devices such as secondary ignition components, motors, generator, etc. These components may induce electrical noise on a circuit that could interfere with normal circuit operation. Electrical system interference caused by a malfunctioning relay, ECM driven solenoid, or switch. They can cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating. Incorrect installation of non-factory, aftermarket, add-on accessories such as lights, 2-way radios, amplifiers, electric motors, remote starters, alarm systems, cell phones, etc. Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode or resistor. |
| Incorrect ECM Programming | There are only a few situations where reprogramming an ECM is appropriate: An ECM from another vehicle is installed. Revised software/calibration files have been released for this vehicle. IMPORTANT: DO NOT reprogram the ECM with the SAME software/calibration files that are already present in the ECM. This is not an effective repair for any type of driveability problem. Verify that the ECM contains the correct software/calibration. If incorrect programming is found, reprogram the ECM with the most current software/calibration. Refer to Service Programming System (SPS) in Programming. |
| Duplicating Failure Conditions | If the previous tests were not successful, attempt to duplicate and/or capture the failure conditions. Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Review and record the Freeze Frame/Failure Records data. Clear any DTCs with a scan tool. Turn OFF the key and wait 15 seconds. Operate the vehicle under the same conditions that were noted in Freeze Frame/Failure Records. The vehicle must also be operating within the Conditions For Running the DTC. Refer to Conditions for Running the DTC in the supporting text of the DTC being diagnosed. Monitor DTC status for the DTC being tested. The scan tool will indicate Ran when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed. An alternate method is to drive the vehicle with a DMM connected to a suspected circuit. An abnormal reading on the DMM when the problem occurs may help you locate the problem. |
| Scan Tool Snapshot | The scan tool can be set up to take a snapshot of the parameters available via serial data. The Snapshot function records live data over a period of time. The recorded data can be played back and analyzed. The scan tool can also graph parameters singly or in combinations of parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed or set up in advance to trigger when a DTC sets. An abnormal value captured in the recorded data may point to a system or component that needs to be investigated further. Refer to the scan tool user instructions for more information on the Snapshot function. |
| IMPORTANT |
|---|
| DO NOT reprogram the ECM with the SAME software/calibration files that are already present in the ECM. This is not an effective repair for any type of driveability problem. |
Hard Start
| Inspection/Test | Action |
|---|
| DEFINITION: Engine cranks OK, but does not start for a long time. Does eventually run, or may start but immediately dies. |
| Preliminary | Refer to Symptoms - Engine Controls . Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Search for bulletins. Verify that the driver is using the correct starting procedure as described in the owners manual. |
| Sensor/System | Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance for resistance specifications. Verify proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . |
| Fuel System | Verify there is adequate fuel. A faulty in-tank sender check valve allows the fuel in the lines to drain back to the tank after the engine stops. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Coil Test . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . Determine the cause of the conditions before replacing the spark plugs. Inspect for loose ignition coil grounds. Inspect the ignition coils for cracks or carbon tracking. Soak the secondary ignition with water may help locate an intermittent problem. Ignition voltage will arc to ground when a secondary component is faulty. |
| Engine Mechanical | Inspect for the following conditions: Excessive oil in combustion chamber or leaking valve seals - Refer Oil Consumption Diagnosis in Engine Mechanical. Cylinder compression - Refer to Engine Compression Test in Engine Mechanical. Improper valve timing Worn rocker arms Broken or worn valve springs Combustion chambers for excessive carbon buildup-Clean the chambers using top engine cleaner. Follow the instructions on the can. Incorrect or damaged basic engine parts-Inspect the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional | Inspect for a restricted exhaust. Refer to Restricted Exhaust in Engine Exhaust. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking, especially between the MAF sensor and the throttle body. |
Surges/Chuggles
| Inspection/Tests | Action |
|---|
| DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the accelerator pedal position. |
| Preliminary | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Verify the driver understands the operation of the transmission torque converter clutch (TCC) and A/C compressor operation as explained in the owners manual. Inform the customer how the TCC and the A/C clutch operates. |
| Sensor/System | NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect the heated oxygen sensors (HO2S). The HO2S should respond quickly to different throttle positions. If they do not, inspect the HO2S for silicon or other contaminates from fuel or the use of improper RTV sealant. The sensors may have a white, powdery coating and result in a high but false signal voltage rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem. Inspect the mass air flow (MAF) sensor for any contamination on the sensing element. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAF sensor and the throttle body. Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary. Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector Engine oil contaminated by fuel - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . An EVAP canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . For proper operation of the manifold absolute pressure (MAP) sensor - Refer to Scan Tool Data Definitions . For proper operation of the mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted - Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure - Refer to Fuel System Diagnosis . Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . For proper operation of the manifold absolute pressure (MAP) sensor - Refer to Scan Tool Data Definitions . For proper operation of the mass air flow (MAF) sensor Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Ignition System | Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water. Test for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. Inspect for loose ignition coil grounds. Inspect the ignition coils for cracks or carbon tracking. |
| Additional Inspections | Visually and physically inspect vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the transmission torque converter clutch (TCC) operation. Test the A/C clutch for proper operation. Refer to Symptoms - HVAC Systems - Automatic in HVAC Systems Automatic. Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust in Engine Exhaust. |
| NOTE |
|---|
| Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Lack of Power, Sluggishness, or Sponginess
| Inspection/Tests | Action |
|---|
| DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way. |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Remove the air filter element and inspect for dirt or for restrictions. Refer to Air Cleaner Element Replacement and replace as necessary. |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Blockage on the inlet screen of the MAF sensor Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted - Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure - Refer to Fuel System Diagnosis . Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data Definitions . Inspect for a dirty or damaged air cleaner element. Inspect for a collapsed or damaged intake air duct. |
| Ignition System | Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as water is applied. Monitor the Misfire Current Counters while driving the vehicle within the conditions that the misfire occurred. Inspect for proper ignition voltage output with the J 26792 Spark Tester. Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Inspect for loose ignition coil ground. |
| Engine Mechanical | Inspect for incorrect camshaft timing. Refer to Setting Camshaft Timing in Engine Mechanical. Inspect for excessive oil in the combustion chambers and leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. Test cylinder compression. Refer to Engine Compression Test in Engine Mechanical. Inspect for incorrect basic engine parts, including the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional Inspections | Inspect the exhaust system for possible restrictions. Refer to Restricted Exhaust in Engine Exhaust. Inspect the exhaust system for damaged or collapsed pipes. Inspect the mufflers for heat distress or internal failure. Inspect the transmission torque converter clutch (TCC) for proper operation. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Lack of Power, Sluggish or Spongy
Detonation/Spark Knock
| Inspection/Tests | Action |
|---|
| DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that changes with throttle opening. |
| Preliminary Inspections | Refer to Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . If there are no engine mechanical faults, fill the fuel tank with a known high quality fuel that meets the vehicles minimum octane requirements. Road test the vehicle and re-evaluate the vehicles performance. |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Inspect for an engine coolant temperature (ECT) sensor that has shifted in value. Refer to Temperature vs Resistance . |
| Ignition System | Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as water is applied. Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . Verify that the spark plugs are of the type. Refer to Ignition System Specifications . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Inspect for loose ignition coil ground. |
| Engine Cooling System | Inspect for obvious overheating conditions: Low engine coolant - Refer to Loss of Coolant in Engine Cooling. A faulty thermostat - Refer to Thermostat Diagnosis in Engine Cooling. Restricted air flow to the radiator or restricted coolant flow through the radiator An inoperative electric cooling fan - Refer to Cooling Fan Inoperative in Engine Cooling. Proper tension on the drive belts - Refer to Drive Belt Tensioner Diagnosis in Engine Mechanical. The correct coolant solution should be a 50/50 mix. Refer to Cooling System Description and Operation in Engine Cooling. |
| Engine Mechanical | Inspect for the following engine mechanical conditions: Excessive oil in combustion chamber-Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. High cylinder compression - Refer to Engine Compression Test in Engine Mechanical. Combustion chambers for excessive carbon buildup-Clean the combustion chamber by using top engine cleaner. Follow the instructions on the can. Incorrect camshaft timing - Refer to Setting Camshaft Timing in Engine Mechanical. Inspect for incorrect basic engine parts. Inspect the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical. |
| Additional Inspections | Inspect the park/neutral position (PNP) switch operation. Inspect the transmission torque converter clutch (TCC) operation. The TCC applying too soon can cause the engine to spark knock. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Hesitation, Sag, Stumble
| Inspection/Tests | Action |
|---|
| DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move, as from a stop. May cause the engine to stall if severe enough. |
| Preliminary | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems, and Engine Controls Schematics . |
| Sensor/System | NOTE: Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. Inspect the heated oxygen sensors (HO2S). The HO2S should respond quickly to different throttle positions. If they do not, inspect the HO2S for silicon or other contaminates from fuel or the use of improper RTV sealant. The sensors may have a white, powdery coating and result in a high but false signal voltage rich exhaust indication. The PCM will then reduce the amount of fuel delivered to the engine causing a severe driveability problem. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAF sensor and the throttle body. Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance for resistance specifications. Inspect the mass air flow (MAF) sensor and intake air system for proper operation. Refer to Scan Tool Data Definitions . |
| Fuel System | Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Test the fuel injector Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector Engine oil contaminated by fuel An EVAP canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted - Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure - Refer to Fuel System Diagnosis . Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Ignition System | Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Test for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and check for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gauge gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Inspect for loose ignition coil ground. Refer to Power and Grounding Component Views in Wiring Systems. |
| Engine Cooling System | Inspect the engine thermostat for proper operation and for correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Engine Mechanical | Inspect for excessive crankshaft endplay that will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance |
| Additional Inspections | Inspect the generator output voltage. Refer to Charging System Test in Engine Electrical. |
| NOTE |
|---|
| Refer to Silicon Contamination of Heated Oxygen Sensors Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Cuts Out, Misses
| Inspections | Action |
|---|
| DEFINITION: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. This condition is not normally felt above 1,500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or low speed. |
| Preliminary | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Verify that the engine control module (ECM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Remove the air filter element and inspect for dirt and for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary. |
| Fuel System | Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for proper operation of the evaporative emission (EVAP) control system. Refer to Evaporative Emission (EVAP) Control System Description . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Engine oil contaminated by fuel An EVAP canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Blockage on the inlet screen of the MAF sensor. Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted - Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure - Refer to Fuel System Diagnosis . Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . Inspect for proper operation of the MAP sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the MAF sensor. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Monitor the knock sensor (KS) system for excessive spark retard activity, with a scan tool. Inspect the air intake ducts for being collapsed, damaged, loose, improperly installed, or leaking especially between the MAF sensor and the throttle body. Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance . Inspect for a vacuum leak. Inspect the crankcase ventilation operation. Refer to Crankcase Ventilation System Inspection/Diagnosis in Engine Mechanical. |
| Ignition System | Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Performing a Cylinder Balance Test with a scan tool may also help isolate which cylinder may be misfiring. Test for proper ignition voltage output. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Correct heat range Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications . Determine the cause of the fouling before replacing the spark plugs. Visually and physically inspect for the following conditions: The spark plug boots for signs of arcing, cracks, carbon tracking, or damage The spark plug boots for proper engagement to spark plug The ignition coils for cracks or carbon tracking |
| Engine Mechanical | Inspect engine mechanical for the following conditions: Test compression - Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms - Refer to Valve Rocker Arms Cleaning and Inspection in Engine Mechanical. Broken valve springs - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. Excessive oil in combustion chamber-Leaking valve seals For more information refer to one of the following procedures: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect basic engine parts inspect the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnostic procedures. |
| Additional Inspections | Inspect the exhaust system for possible restrictions. Inspect for the following conditions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters- Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine misfire condition. A sudden increase in indicated RPM with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components near ignition control circuits if a condition exists. Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection or Exhaust Manifold Cleaning and Inspection - Left and Exhaust Manifold Cleaning and Inspection - Right in Engine Mechanical |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Poor Fuel Economy
| Inspections | Action |
|---|
| DEFINITION: Fuel economy, as measured by an actual road test, is noticeably lower than expected. Also, fuel economy is noticeably lower than the economy was on this vehicle at one time, as previously shown by an actual road test. |
| Preliminary | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . Discuss driving habits with the owner. Is the A/C ON or the Defroster mode ON full time? Are the tires at the correct pressure? Are the wheels and tires the correct size? Are there excessively heavy loads being carried? Is the acceleration rate too much, too often? Remove the air filter element and inspect for dirt or for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary. |
| Fuel System | Discuss with the owner the type, quality, and alcohol content of the fuel. Oxygenated fuels have lower energy and may deliver reduced fuel economy. Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Test for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Inspect that each fuel injector harness is connected to the correct injector and cylinder. Relocate the injector harnesses as necessary. Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . For proper operation of the manifold absolute pressure (MAP) sensor - Refer to Scan Tool Data Definitions . For proper operation of the mass air flow (MAF) sensor Blockage on the inlet screen of the MAF sensor Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted - Refer to Air Cleaner Element Replacement . |
| Sensor/System | Inspect the air intake system and crankcase for air leaks. Verify that the engine coolant temperature (ECT) sensor is not shifted in value. Refer to Temperature vs Resistance for resistance specifications. Inspect for an inaccurate speedometer. Refer to Symptoms - Instrument Panel, Gages and Console in Instrument Panel, Gages, and Console. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data Definitions . |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Remove the spark plugs and inspect for the following conditions: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Spark Plug Replacement and Ignition System Specifications . Determine the cause of the fouling before replacing the spark plugs. Soaking the secondary ignition system with water from a spray bottle may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. Inspect for loose ignition coil grounds. Refer to Power and Grounding Component Views in Wiring Systems. |
| Engine Cooling System | Inspect the engine coolant level for being low. Refer to Loss of Coolant in Engine Cooling. Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Engine Mechanical | Inspect engine mechanical for the following conditions: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber-Leaking valve seals. For more information refer to one of the following procedures: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect basic engine parts inspect for the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnostic procedures. |
| Additional Inspections | Visually and physically check the vacuum hoses for splits, kinks, and proper connections and routing as shown on Vehicle Emission Control Information label. Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate a RPM drop, when the system commands the TCC ON. Inspect the exhaust system for a possible restriction. Inspect for the following conditions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters - Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates EMI is present. Inspect for high voltage components, near ignition control circuits, if a condition exists. Inspect the brake system for dragging or improper operation. Refer to Symptoms - Hydraulic Brakes in Hydraulic Brakes. Verify that the vehicle operator does not drive with a foot on the brake pedal. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Poor Fuel Fill Quality
| Problem | Causes |
|---|
| Definition: During the fueling process a continual, occasional or no fuel nozzle shut-off condition has occurred. |
| Difficult to fill | Fill limiter vent valve stuck closed Evaporative emission (EVAP) canister restricted EVAP vent valve stuck closed Restricted vapor lines High Reid vapor pressure or high fuel temperature Fuel filler hose is pinched or kinked Ignition switch ON |
| Over fill | Pressure relief valve is stuck open or leaking Fill limiter vent valve stuck open or leaking |
| Pre-mature shut-off of the fuel dispensing nozzle | Fill limiter vent valve stuck closed EVAP canister restricted EVAP vent valve stuck closed Restricted vapor lines High Reid vapor pressure or high fuel temperature Ignition switch ON (EVAP vent valve closed) |
| Fuel Spitback | Restricted EVAP canister High Reid vapor pressure or high fuel temperature Ignition switch ON |
Rough, Unstable, or Incorrect Idle and Stalling
| Inspections | Action |
|---|
| DEFINITION: Engine runs unevenly at idle. If severe, the engine or vehicle may shake. Engine idle speed may vary in RPM. Either condition may be severe enough to stall the engine. |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems. Remove and inspect the air filter element for dirt or for restrictions. Refer to Air Cleaner Element Replacement . Replace as necessary. |
| Fuel System | Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool or Fuel Injector Coil Test . Inspect for incorrect fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Inspect that each fuel injector harness is connected to the correct injector/cylinder. Relocate fuel injector harnesses as necessary. Inspect for the following conditions that may cause the engine to run rich: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the heated oxygen sensor (HO2S) connector Engine oil contaminated by fuel An evaporative emission (EVAP) canister purge condition Incorrect fuel pressure - Refer to Fuel System Diagnosis . Leaking fuel injectors - Refer to Fuel System Diagnosis . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the mass air flow (MAF) sensor. Refer to Scan Tool Data Definitions . Blockage on the inlet screen of the MAF sensor Vacuum hoses that are split, kinked, or improperly connected An air intake duct that is collapsed or restricted An air filter that is dirty or restricted - Refer to Air Cleaner Element Replacement . Inspect for the following conditions that may cause the engine to run lean: NOTE: Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. Water intrusion in the HO2S connector An exhaust leak between the HO2S and the engine - Refer to Exhaust Leakage in Engine Exhaust. Vacuum leaks Incorrect fuel pressure - Refer to Fuel System Diagnosis . Restricted fuel injectors - Refer to Fuel Injector Balance Test with Special Tool . Inspect for proper operation of the manifold absolute pressure (MAP) sensor. Refer to Scan Tool Data Definitions . Inspect for proper operation of the MAF sensor. Refer to Scan Tool Data Definitions . Fuel contamination - Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Vacuum hoses that are split, kinked, or improperly connected |
| Sensor/System | Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body. Inspect the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. Refer to Scan Tool Data Definitions . |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis for the procedure. Remove spark plugs and check for the following conditions: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits In order to properly inspect the spark plugs or to correct a condition, refer to the following procedures: Ignition System Specifications Spark Plug Inspection Spark Plug Replacement An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Determine the cause of the fouling before replacing the spark plugs. Inspect the spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Inspect for loose ignition coil grounds. Refer to Power and Grounding Component Views in Engine Electrical. |
| Engine Mechanical | Inspect engine mechanical for the following conditions: Compression Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals For more information, refer to one or more of the following procedures in Engine Mechanical: Engine Compression Test Symptoms - Engine Mechanical Oil Consumption Diagnosis For incorrect basic engine parts. Inspect the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Inspect for excessive crankshaft endplay that will cause the crankshaft position (CKP) sensor reluctor wheel to move out of alignment with the CKP sensor. Refer to Crankshaft and Bearings Cleaning and Inspection in Engine Mechanical. This could result in any of the following conditions: A no start A start and stall Erratic performance Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. |
| Additional Inspections | Inspect the exhaust system for the following possible restrictions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters - Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change indicates that EMI is present. If a problem exists, inspect routing of high voltage components near the ignition control circuits. Inspect for faulty motor mounts. Refer to Engine Mount Inspection in Engine Mechanical. Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection , or Exhaust Manifold Cleaning and Inspection - Left and Exhaust Manifold Cleaning and Inspection - Right in Engine Mechanical. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
| NOTE |
|---|
| Refer to Heated Oxygen and Oxygen Sensor Notice in Cautions and Notices. |
Rough, Unstable, or Incorrect Idle and Stalling
Dieseling, Run-On
| Inspections | Action |
|---|
| DEFINITION: Engine continues to run after key is turned OFF, but runs very rough. If the engine runs smooth, inspect the ignition switch and the ignition switch adjustment. |
| Preliminary Inspections | Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls . Search for bulletins. Verify that the engine control module (ECM) grounds are clean, tight, and in the proper locations. Refer to Power and Grounding Component Views in Wiring Systems and Engine Controls Schematics . |
| Fuel System | Test the fuel injectors. Refer to Fuel Injector Balance Test with Special Tool and Fuel Injector Coil Test . |
| Additional Inspections | Remove the spark plugs and inspect for the following conditions: Correct heat range Heavy deposits Refer to Spark Plug Inspection . |
Backfire
| Inspections | Actions |
|---|
| DEFINITION Fuel ignites in the intake manifold or in the exhaust system, making a loud popping noise. |
| Preliminary Inspections | Refer to Symptoms - Engine Controls . Search for bulletins. Inspect the engine control module (ECM) grounds for being clean, tight, and in the proper locations. Refer to Power and Grounding Component Views and Engine Controls Schematics in Wiring Systems. |
| Fuel System | Test for correct fuel pressure. Refer to Fuel System Diagnosis . Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (W/Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (W/O Special Tool) . Verify that each injector harness is connected to the correct injector or cylinder. Relocate injector harnesses as necessary. |
| Sensor/System | Inspect the air intake system and crankcase for air leaks. Use a scan tool in order to monitor the knock sensor (KS) system for excessive spark retard activity. |
| Ignition System | Inspect for proper ignition voltage output with the J 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis . Inspect the coils for cracks, carbon tracking/arcing. Inspect spark plug boots for signs of arcing, cracks, carbon tracking, or damage. Remove spark plugs and inspect for the following conditions: Wet plugs Cracks Wear Improper gap Burned electrodes Heavy deposits Refer to Spark Plug Inspection . An improper spark plug gap will cause a driveability problem. Gap the spark plugs using a wire gage gap tool. Refer to Ignition System Specifications and Spark Plug Replacement . Determine the cause of the fouling before replacing the spark plugs. Soak the secondary ignition system with water from a spray bottle. Soaking the secondary ignition system may help locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply the water. Monitor the Misfire Current Counters while driving the vehicle in the conditions that the misfire occurred. Inspect for loose ignition coil ground. Refer to Power and Grounding Component Views in Engine Electrical. |
| Engine Cooling System | Inspect the engine coolant level for being low. Refer to Loss of Coolant in Engine Cooling. Inspect the engine thermostat for proper operation and for the correct heat range. Refer to Thermostat Diagnosis in Engine Cooling. |
| Engine Mechanical | Inspect engine mechanical for the following conditions: Compression - Refer to Engine Compression Test in Engine Mechanical. Sticking or leaking valves Worn camshaft lobes Valve timing Worn rocker arms Broken valve springs Excessive oil in combustion chamber or leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical. For incorrect basic engine parts. Inspect the following components: The camshaft - Refer to Camshaft Cleaning and Inspection in Engine Mechanical. The cylinder heads - Refer to Cylinder Head Cleaning and Inspection in Engine Mechanical. The pistons, etc. - Refer to Piston, Connecting Rod, and Bearings Cleaning and Inspection in Engine Mechanical. Refer to Symptoms - Engine Mechanical in Engine Mechanical for diagnosis procedures. |
| Additional Inspections | Visually and physically inspect the vacuum hoses for splits, kinks, and proper connections and routing as shown on the Vehicle Emission Control Information label. Inspect the intake manifold and the exhaust manifold passages for casting flash. Refer to Intake Manifold Cleaning and Inspection or Exhaust Manifold Cleaning and Inspection - Left and Exhaust Manifold Cleaning and Inspection - Right in Engine Mechanical. Inspect the transmission torque converter clutch (TCC) operation. The scan tool should indicate an RPM drop when the TCC is commanded ON. Inspect the exhaust system for possible restrictions. Inspect the following conditions: The exhaust system for damaged or collapsed pipes The mufflers for heat distress or possible internal failure For possible plugged catalytic converters - Refer to Restricted Exhaust in Engine Exhaust. Electromagnetic interference (EMI) on the reference circuit can cause an engine miss condition. A scan tool can usually detect EMI by monitoring the engine RPM. A sudden increase in RPM with little change in actual engine RPM change may indicate that EMI is present. If a problem exists, inspect for high voltage components near the ignition control circuits. |
Conditions for Updating the I/M System Status
Each system monitor requires at least one, and sometimes several diagnostic tests. The result of each test is reported by a diagnostic trouble code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or when any one of the DTCs comprising the monitor has illuminated the malfunction indicator lamp (MIL). Once the system monitor is complete, the I/M System Status display will indicate YES in the Completed column.
For example, when the HO2S Heater Status indicates YES, either all of the oxygen sensor heater tests have passed or one of the tests has illuminated the MIL. If the vehicle has 4 heated oxygen sensors, either all 4 heater circuit tests have passed or one of the heater circuit tests has illuminated the MIL. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO
- The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
- The battery has been disconnected or discharged below operating voltage.
- The control module power or ground has been interrupted.
- The control module has been reprogrammed.
- The control module DTCs have been cleared as part of a service procedure.
Monitored Emission Control Systems
The OBD II System monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with secondary air injection (AIR) or exhaust gas recirculation (EGR). The OBD II regulations require monitoring of the following
- The air conditioning system
- The catalytic converter efficiency
- Comprehensive component monitoring-Emission related inputs and outputs
- The evaporative emissions (EVAP) system
- The EGR System
- The fuel delivery system
- Heated catalyst monitoring
- Misfire monitoring
- The oxygen sensor system (O2S or HO2S)
- The oxygen sensor heater system (HO2S heater)
- The AIR system
For the specific DTCs required for each system, refer to Inspection/Maintenance (I/M) System DTC Table . Systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously and do not require an I/M System Status indicator.
| Step | Action | Value(s) | Yes | No |
|---|
| 1 | Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information. IMPORTANT: Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure. Repair any DTCs or driveability concerns that would prevent the I/M System Status tests from completing. Did you find and repair a DTC or driveability concern? | | Go to Step 3 | Go to Step 2 |
| 2 | Review any service bulletins for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by the service bulletins. Was a reprogramming or repair service required? | | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | Go to Step 3 |
| 3 | Observe the I/M System Status display with a scan tool. Is more than one test indicating a NO status? | | Go to Inspection/Maintenance (I/M) Complete System Set Procedure | Go to the I/M System Set Procedure for the indicated system |
| IMPORTANT |
|---|
| Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete System Set Procedure. |
Inspection/Maintenance (I/M) System Check
