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Engine Controls - Tests W/o Codes Chevrolet Beretta I

Testing & Diagnostics ~4704 words

INTRODUCTION

Before attempting to diagnose symptoms or intermittent faults, ensure steps in BASIC TESTING and appropriate SELF-DIAGNOSTICS articles have been performed. Use this article to diagnose driveability problems that exist when a hard fault code is not present.

Symptom checks are intended to direct the technician to malfunctioning component(s) so that further diagnosis may be performed. A "symptom" should lead to further testing of specific components or systems, or verification of adjustment specifications.

Use intermittent test procedures to locate intermittent driveability problems that do not occur when the vehicle is being tested. These problems may cause a noticeable driveability problem or cause the "malfunction" warning light to illuminate on some vehicles.

It is also possible that certain driveability concerns have been rectified by the manufacturer through substitution of a revised calibration chip or computer control unit. Check with manufacturer for latest information on updated chips and control units.

Note. For specific testing procedures, refer to the article SYSTEM/COMPONENT TESTS article. For verifying specifications, refer to the following articles

  1. «ADJUSTMENTS - 4-CYL»(/chevrolet/beretta/i-1987-1996/remont/adjustments/#engine-controls-adjustments-4-cyl)
  2. «ADJUSTMENTS - V6»(/chevrolet/beretta/i-1987-1996/remont/adjustments/#engine-controls-adjustments-v6)
  3. «ADJUSTMENTS - V8»(ref-10188)

Or

  1. «SPECIFICATIONS - 4-CYL»(/chevrolet/beretta/i-1987-1996/remont/specifications/#engine-controls-specifications-4-cyl)
  2. «SPECIFICATIONS - V6»(/chevrolet/beretta/i-1987-1996/remont/specifications/#engine-controls-specifications-v6)
  3. «SPECIFICATIONS - V8»(ref-10187)

PRELIMINARY CHECKS

This portion of article is used only AFTER you have checked the following

  1. Verify the on-car diagnostics are working by performing DIAGNOSTIC CIRCUIT CHECK located in «BASIC TESTING»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article.
  2. Verify that the ECM and "SERVICE ENGINE SOON" light are functioning properly.
  3. Verify that there are no trouble codes stored, or only intermittent ones.
  4. Verify that the fuel control system is operating properly by performing appropriate SYSTEM PERFORMANCE CHECK chart (carbureted models), FIELD SERVICE MODE CHECK (fuel injected models except Cadillac) or PFI SYSTEM CHECK (Cadillac except Brougham) located in «BASIC TESTING»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article.
  5. Perform fuel system pressure test on EFI vehicles.
  6. Perform a careful visual inspection of all systems.

After all checks have been performed, verify customer complaint and locate correct symptom. Check items indicated under that symptom. Not all items listed under each symptom apply to all models and systems. These procedures will normally recommend testing of a system or component on vehicle, such as EGR, EST, TCC, etc. These are covered in the SYSTEM/COMPONENT TESTS article.

Note. On TBI and PFI vehicles, if ECM displays data but engine fails to start, proceed to NO START - ENGINE CRANKS OKAY, in the BASIC TESTING article.

SYMPTOM DEFINITION

Engine cranks, but does not start for a long time. Eventually, engine does run. If engine starts but immediately dies (as soon as key is released), refer to the NO START - ENGINE CRANKS OKAY in procedures in the BASIC TESTING article.

Possible Cause & Correction

Check the following items

  1. Ensure driver is using proper starting procedure.
  2. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both distributor cap and spark plugs.
  3. Check for air leaks at carburetor mounting and intake manifold.
  4. Check wires for pinches, cuts, and proper connections.
  5. Check choke valve, throttle and fast idle cam for sticking. Replace any malfunctioning parts. If caused by foreign material and gum, clean with non-oil base solvent.
  6. Check choke and vacuum break operation adjustment.
  7. Check EGR valve system for faulty operation that could cause valve to stick open.
  8. Check float level using external float gauge. Adjust float to specification, if required.
  9. Check carburetor fuel inlet filter. Replace if required.
  10. Check ignition system.
  11. Check distributor for worn shaft, bare and shorted wires, pick-up coil resistance and connections, loose ignition coil ground, and moisture in distributor cap.
  12. Remove spark plugs and check for wet plugs, wear, improper gap, burned electrodes or heavy deposits. Clean or replace as necessary.
  13. Check ignition timing and adjust if necessary.
  14. Check fuel pump pressure, volume and vacuum

Engine cranks, but does not start for a long time. Eventually, engine does run. If engine starts but immediately dies (as soon as key is released), see NO START - ENGINE CRANKS OKAY in the appropriate BASIC TESTING article.

Check the following items

  1. Ensure driver is using proper starting procedure.
  2. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both distributor cap and spark plugs.
  3. Check wires for pinches, cuts, and proper connections.
  4. Check choke valve, throttle and fast idle cam for sticking. Replace any malfunctioning parts. If caused by foreign material and gum, clean with non-oil base solvent.
  5. Check choke and vacuum break operation adjustment.
  6. Check EGR valve system for faulty operation that could cause valve to stick open.
  7. Check for carburetor flooding.
  8. Check float level using external float gauge. Adjust float to specification, if required.
  9. Check carburetor fuel inlet filter. Replace if required.
  10. Check for obvious overheating problems.
  11. Check EFE system operation as described in the article «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) . EFE valve should be open.
  12. Check ignition system.
  13. Check distributor for worn shaft, bare and shorted wires, pick-up coil resistance and connections, loose ignition coil ground, and moisture in distributor cap.
  14. Remove spark plugs and check for wet plugs, wear, improper gap, burned electrodes or heavy deposits. Clean or replace as necessary.
  15. Check ignition timing and adjust if necessary.

Engine cranks okay, but does not start for a long time. Engine eventually starts, may immediately die or run okay.

Check the following items

  1. Check fuel pump relay. To do this, connect test light between fuel pump test terminal (terminal "G" of ALDL on most vehicles) and ground. Turn ignition on. Light should illuminate for 2 seconds. If not, see FUEL PUMP RELAY in the article «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) . For location of fuel pump test connector, see COMPONENT LOCATIONS in the article «I - SYSTEM/COMPONENT LOCATIONS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#systemcomponent-locations) .
  2. Check for poor quality or water contaminated fuel.
  3. Check that TPS is not sticking or binding.
  4. Check EGR operation.
  5. Check for a leaking injector. To do this on TBI systems, disconnect injector electrical connector at injector. Crank engine and watch for fuel leakage.
  6. Check that resistance of coolant sensor circuit or coolant sensor is not too high. See CODE 15 chart in appropriate TESTS W/CODES article, or the «SENSOR RANGE CHARTS»(/chevrolet/beretta/i-1987-1996/remont/sensor-range-charts/#engine-controls-sensor-operating-range-charts) article.
  7. Check ignition system for a worn distributor shaft, bare or shorted wires, incorrect pick-up coil resistance, loose ignition coil ground or moisture in distributor cap. Check for adequate spark using Spark Tester (ST-125).
  8. Check for shorts by spraying plug wires with fine mist of water.
  9. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
  10. Check for correct fuel pressure in all speed ranges.
  11. A faulty in-tank fuel pump check valve will allow fuel in lines to drain back to tank after engine is stopped. To check this condition, turn ignition off, disconnect fuel pressure line at fuel rail, remove filler cap, and connect a radiator test pump and apply 15 psi (1.0 kg/cm 2 ) pressure. If pressure will hold for 60 seconds, check valve is okay.
  12. Check that PROM/MEM-CAL in vehicle is correct for that vehicle. See ECM/PROM under ENGINE PERFORMANCE for latest application information.
  13. Check for restricted exhaust system.

This condition is with engine in warm-up mode at room or outside temperature, within 3 minutes after start. Vehicle stalls after brief idle, dies as soon as any load is placed on engine (such as A/C turned on or transmission engaged) or dies on initial driveaway. If symptom is present when vehicle is both cold and hot, go to symptom STALL AFTER START - HOT.

Check the following items

  1. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label (in engine compartment).
  2. Make sure hot air tube is connected to air cleaner.
  3. Check for proper operation of thermostatic air cleaner.
  4. Check choke valve, throttle and fast idle cam for sticking. Replace any malfunctioning parts. If caused by foreign material and gum, clean with non-oil base solvent.
  5. With engine off, check all choke adjustments, including vacuum breaks and TVS if used.
  6. Check carburetor accelerator pump operation.
  7. Check fast idle speed and curb idle speed if applicable.
  8. Check EFE system for proper operation. EFE vacuum valve should be closed when cold.
  9. Check choke and vacuum break operation adjustment.
  10. Check EGR valve system for sticky operation that could cause valve to stick open.
  11. Check ignition timing and adjust if necessary.
  12. Check for poor or contaminated gasoline.

This condition is with engine in warm-up mode at room or outside temperature, within 3 minutes after start. Vehicle stalls after brief idle, dies as soon as any load is placed on engine (such as A/C turned on or transmission engaged) or dies on initial driveaway.

Check the following items

  1. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label.
  2. Make sure hot air tube is connected to air cleaner.
  3. Check for proper operation of thermostatic air cleaner.
  4. Check choke valve, throttle and fast idle cam for sticking. Replace any malfunctioning parts. If caused by foreign material and gum, clean with non-oil base solvent.
  5. With engine off, check all choke adjustments, including vacuum breaks and TVS if used.
  6. Check carburetor accelerator pump operation.
  7. Check fast idle speed and curb idle speed if applicable.
  8. Check EFE system for proper operation. EFE valve should be open.
  9. Check choke and vacuum break operation adjustment.
  10. Check EGR valve system for faulty operation that could cause valve to stick open.
  11. Check ignition timing and adjust if necessary.
  12. Check for poor or contaminated gasoline.
  13. Check for obvious overheat condition.
  14. Check for overcharged A/C system.
  15. Check operation of power steering cut-out switch.

Engine starts okay but dies after brief idle, dies as soon as any load is placed on engine (such as turning on air conditioner or engaging transmission), or on initial driveaway.

Check the following items

  1. Make sure that hot air tube is connected to air cleaner.
  2. Check for proper operation of thermostatic air cleaner.
  3. Check for proper operation of Idle Air Control (IAC) system.
  4. Check PCV valve for proper operation.
  5. Unplug MAF or MAP sensor. ECM will substitute a default value for sensor signal. If stall condition is eliminated, replace sensor.
  6. Check EGR system for proper operation.
  7. If stall occurs when air conditioner is turned on, check for air conditioner clutch signal to ECM terminal. Voltage at A/C terminal of ECM should be battery voltage when air conditioner compressor clutch is engaged. A high voltage surge due to a shorted compressor clutch diode could cause ECM shutdown.
  8. Check for an overcharged air conditioner system.
  9. Check for plugged or restricted fuel lines.
  10. Using Spark Tester (ST-125), check for a weak spark from ignition coil.

This is defined as a momentary lack of response as accelerator is pushed down. It can occur at all vehicle speeds. Usually, it is most severe when first trying to make vehicle move. Occasionally, this condition may cause vehicle to stall.

Check the following items

  1. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both distributor cap and spark plugs.
  2. Check wires for pinches, cuts, and proper connections.
  3. Make sure hot air tube is connected to air cleaner.
  4. Check for proper operation of thermostatic air cleaner.
  5. Check float level using external float gauge. Adjust float to specification, if required.
  6. With engine off, check all choke adjustments, including vacuum breaks and TVS if used.
  7. Check carburetor accelerator pump operation.
  8. Check fast idle speed and curb idle speed, if applicable.
  9. Check EFE system for proper operation. EFE valve should be closed.
  10. Check vacuum hose to pressure sensor for leaks, restrictions and proper connections (should be manifold vacuum).
  11. Check EGR valve operation.
  12. Check TPS adjustment. See «ADJUSTMENTS - 4-CYL»(/chevrolet/beretta/i-1987-1996/remont/adjustments/#engine-controls-adjustments-4-cyl) , «ADJUSTMENTS - V6»(/chevrolet/beretta/i-1987-1996/remont/adjustments/#engine-controls-adjustments-v6) or «ADJUSTMENTS - V8»(ref-10188)
  13. Check canister purge system.
  14. Check for open ignition coil ground and for intermittent ECM ground.
  15. Check engine ignition timing.
  16. Check for poor quality or contaminated gasoline.

Momentary lack of response when accelerator is pushed down. Can occur at all vehicle speeds. Usually occurs when taking off from a stop.

Check the following items

  1. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label. Check ignition wires for cracking, hardness and proper connections at both distributor cap and spark plugs.
  2. Check wires for pinches, cuts, and proper connections.
  3. Check that fuel pressure is correct in all speed ranges. Also check for poor quality or water contaminated fuel.
  4. Check for fouled spark plugs.
  5. Check that PROM/MEM-CAL in vehicle is correct for that vehicle. See ECM/PROM under ENGINE PERFORMANCE for latest application information.
  6. Check for a binding or sticking TPS.
  7. Make sure that initial ignition timing is properly set.
  8. Make sure that ECM controlled idle speed is correct.
  9. Check EGR system for proper operation.
  10. Disconnect fuel injector electrical connectors. Crank engine and check for injector leaks.
  11. Check for an open in HEI ground circuit.
  12. Check canister purge system for proper operation.
  13. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
  14. On PFI vehicles, perform INJECTOR BALANCE TEST in the appropriate «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article.

Engine power varies under steady throttle or cruise. Feels like vehicle speeds up and slows down without changing position of accelerator pedal.

Check the following items

  1. Check operation of thermostatic air cleaner damper door.
  2. Check that Park/Neutral switch is properly adjusted.
  3. Check for intermittent open or short to ground in Torque Converter Clutch (TCC) or HEI by-pass circuits.
  4. Check for proper operation of canister purge system.
  5. Check for proper operation of ESC system.
  6. Check for proper operation of EGR system.
  7. Make sure that initial ignition timing is properly set.
  8. Check for adequate spark output using Spark Tester (ST-125).
  9. Check O2 sensor for lead or RTV sealant contamination. This will cause a false high voltage signal to ECM. ECM will respond by leaning air/fuel ratio.
  10. Check in-line fuel filter and replace if dirty or clogged.
  11. Check fuel for water contamination. On carbureted models, check fuel pressure, volume and fuel pump vacuum. On EFI models, check that fuel system pressure is correct at all engine speeds.
  12. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also check condition of distributor cap, rotor and spark plug wires.
  13. Check A/C for excessive charge.
  14. Check for restricted exhaust system.

Engine delivers less power than expected. Little or no increase in speed when accelerator is pushed down.

Check the following items

  1. Check that air filter and fuel filter are not plugged. Replace if necessary. Check for incorrect fuel pressure.
  2. Check for proper operation of thermostatic air cleaner damper door.
  3. Check for proper float level using external gauge (carbureted).
  4. Make sure that initial ignition timing is properly set.
  5. Check for proper operation of TCC or VCC system.
  6. Check ESC system for excessive retard.
  7. Check EST system for proper operation.
  8. Make sure that EGR valve is not open all the time.
  9. Check for proper operation of EFE valve (carbureted).
  10. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See RESTRICTED EXHAUST SYSTEM CHECK in the «BASIC TESTING»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article.
  11. Check charging system output. Repair charging system if voltage is less than 9 volts or more than 16 volts.
  12. Check MAP or pressure sensor output.
  13. Using Spark Tester (ST-125), check for available secondary voltage.
  14. Check engine valve timing and compression.
  15. Check engine for a worn camshaft.

Fuel ignites in intake manifold or in exhaust system making a loud popping noise.

Check the following items

  1. Check for proper valve timing.
  2. Check for engine vacuum leaks and/or engine not tuned to specifications.
  3. Check for faulty air injection divert valve or check valve.
  4. Check for electric air switching valve or air divert valve not switching air pump discharge to air cleaner during engine starting or deceleration.
  5. Check engine for sticking or leaking valves.
  6. Check for fuel or water in vacuum hose to MAP sensor. Also check for restricted hose.
  7. Using Spark Tester (ST-125), check available output voltage of ignition coil.
  8. Check for crossfire between spark plugs, distributor cap and spark plug wires.
  9. Check for an intermittent ignition system problem.
  10. Make sure that initial ignition timing is properly set.

Cuts out, misses is defined as a steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. The exhaust may have a steady spitting sound at idle or low speed. Perform a careful visual inspection as described in the appropriate BASIC TESTING article.

Check the following items

  1. Check ignition wires for short or faulty insulation.
  2. Check Distributor cap (if equipped) for moisture, dust or cracks. Spray spark plug wires with a fine mist of water to check for shorts.
  3. Connect Spark Tester ST-125 to spark plug and check for adequate spark.
  4. Check ignition system for faulty grounds.
  5. Check that EST wiring harness is not routed too close to wiring which may cause induced voltage signals.
  6. Check ignition coil connections.
  7. Remove spark plugs and check for correct heat range, wear, cracks, wetness, improper gap or heavy deposits.
  8. Check for poor or contaminated (water) fuel.
  9. Check for improper fuel pressure.
  10. Check float level on carbureted vehicles.
  11. Using INJECTOR BALANCE TEST located in «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article, check fuel injected vehicles for plugged injectors.
  12. Check for EGR valve sticking open.
  13. Check ECM for proper ground circuits.
  14. TPS for sticking or binding. TPS voltage should be less than 1.25 volts at idle.
  15. Check for proper crank angle sensor (DIS and IDI) or pick-up coil (HEI distributor) resistance.
  16. Check for restricted exhaust as described in «BASIC TESTING»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article.
  17. Check for bent push rods, broken valve springs or worn camshaft lobes.

MISFIRE ISOLATION (FUEL INJECTION)

  1. Start engine. Disconnect IAC motor. Using insulated pliers, remove one spark plug wire from a spark plug and ground it against the engine.
  2. Note engine RPM as wire is grounded. Reconnect spark plug wire. Repeat procedure for all cylinders. Stop engine and reconnect IAC motor.

If engine speed dropped equally (within 50 RPM) on all cylinders, refer to ROUGH, UNSTABLE OR INCORRECT IDLE symptom. If there was no engine RPM drop or excessive variation on one or more cylinder, check spark on the respective cylinder(s).

Engine runs unevenly at idle. If bad enough, vehicle will shake. Idle may vary in RPM. Engine idles at incorrect RPM.

Check the following items

  1. Make sure that throttle linkage and/or TPS are not sticking or binding.
  2. Make sure that initial ignition timing is properly set.
  3. Check engine idle speed, both base idle and ECM idle.
  4. Check Idle Air Control (IAC) system. Check for foreign material in IAC bore. See DIAGNOSTIC AIDS in CODE 35 chart in the appropriate TESTS W/CODES article.
  5. Check for proper operation of EGR system.
  6. Check ISC/ILC operation.
  7. Check P/N switch circuit. Also make sure that P/N switch is properly adjusted.
  8. Check power steering pressure switch circuit.
  9. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See RESTRICTED EXHAUST SYSTEM CHECK in the «BASIC TESTING»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article in this section below.
  10. If rough idle only occurs when engine is hot, check PCV valve for proper operation, check evaporative emission control system, check for proper spark plug gap and check engine compression.

Defined as engine starts okay, but dies at idle. Engine will run if accelerator is held at part throttle.

Check the following items

  1. Visually check vacuum hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label.
  2. Check for air leaks at carburetor mounting and intake manifold.
  3. Check carburetor for flooding.
  4. Check float level using external float gauge.
  5. Check engine idle speed, both base and ECM controlled.
  6. Check EGR system. Check for loose valve or sticking plunger. The EGR system should not function at idle. Pulse width modulated systems do not work in Park or Neutral.
  7. Check carburetor idle adjustment. If unable to adjust, check carburetor idle system.
  8. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter.
  9. Check spark plug condition and gap.

Engine starts but will not run at idle. Engine will run if accelerator is held at part throttle.

Check the following items

  1. Problem is most likely in Idle Air Control (IAC) system. See DIAGNOSTIC AIDS in CODE 35 chart in the appropriate TESTS W/CODES article.
  2. Check EGR system.
  3. Check P/N switch.
  4. On PFI vehicles, perform INJECTOR BALANCE TEST located in «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article.
  5. Disconnect MAF or MAP sensor. If condition is corrected, replace sensor.

Fuel economy, as measured by an actual road test, is noticeably lower than expected. Fuel economy is noticeably lower than was on this vehicle at one time.

Check the following items

  1. Check for proper operation of thermostatic air cleaner damper door. Also check for a clogged air filter.
  2. Check cooling system thermostat for proper heat range and operation.
  3. Check coolant sensor for shift in calibration. Use temperature-to-resistance table in the «SENSOR RANGE CHARTS»(/chevrolet/beretta/i-1987-1996/remont/sensor-range-charts/#engine-controls-sensor-operating-range-charts) article.
  4. Make sure that speedometer is properly calibrated.
  5. Check engine compression.
  6. Check for dragging brakes.
  7. Check A/C for "full time" operation.
  8. Make sure that initial ignition timing is properly set and check for proper EST and ESC operation.
  9. Check for proper operation of TCC or VCC.
  10. Check air pump output not shifting to catalytic converter upon signal from TVS and/or faulty electrical and/or vacuum circuits.
  11. Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See RESTRICTED EXHAUST SYSTEM CHECK in «BASIC TESTING»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-basic-testing) article.
  12. Check oxygen sensor for silicone or lead contamination.
  13. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
  14. Make sure that speedometer is properly calibrated.
  15. Check engine compression.
  16. Check for dragging brakes.

Engine continues to run after ignition is turned off but runs very rough. If engine runs smoothly, check ignition switch.

Check the following items

  1. Check for binding throttle linkage.
  2. Check for leaking injectors on EFI vehicles. On PFI vehicles, perform INJECTOR BALANCE TEST located in the article «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) .
  3. Check IAC (EFI) system. See DIAGNOSTIC AIDS in CODE 35 chart in the appropriate TESTS W/CODES article.
  4. Check ILC (carb.) for proper operation. Testing is located in «SYSTEM/COMPONENT TESTS»(/chevrolet/beretta/i-1987-1996/remont/testing-diagnostics/#engine-controls-systemcomponent-tests) article.
  5. Check engine for overheating.

A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with amount of acceleration.

Check the following items

  1. Check for obvious overheating problems.
  2. Make sure that initial timing is correct.
  3. Check TPS adjustment and operation.
  4. On fuel injected models, check fuel system for low pressure or volume. Also check for induction air leaks.
  5. Make sure that ESC system is operating properly.
  6. Make sure that EGR valve is not open all the time.
  7. Make sure that TCC or VCC system is operating properly.
  8. Make sure that correct PROM is installed in ECM.
  9. Remove carbon from engine with top engine cleaner.
  10. If excessive carbon exists in combustion chamber, check for excessive oil burning due to leaking valve guide seals.
  11. Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
  12. Check that PROM/MEM-CAL in vehicle is correct for that vehicle. See ECM/PROM under ENGINE PERFORMANCE for latest application information.

Vehicle fails emission test. Vehicle may also have excessive "rotten egg" smell (hydrogen sulfide) being emitted from exhaust pipe.

Check the following items

  1. Check for lead contamination of catalytic converter. Look for removal/tampering at restrictor in fuel filler neck.
  2. Check that air is not being diverted to exhaust manifold during normal engine operation and that air is being diverted to catalytic converter during normal engine operation.
  3. If emission test shows excessive carbon monoxide (CO) and hydrocarbons (HC) emissions and vehicle also has excessive odor being emitted, check all systems and components that could cause engine to run rich. See DIAGNOSTIC AIDS in the CODE 45 chart in the appropriate TESTS W/CODES article.
  4. If emission test shows excessive oxides of nitrogen (NOx) emissions, check all systems and components that could cause engine to run lean or to run too hot. See DIAGNOSTIC AIDS in the CODE 44 chart in the appropriate TESTS W/CODES article in table above.

INTERMITTENT PROBLEM DIAGNOSIS

Intermittent fault testing requires the duplication of circuit or component failure, in order to identify the fault. These procedures may lead to the computer recording a fault code (on some systems) which may help in diagnosis.

If problem vehicle does not produce fault codes, it will be necessary to monitor voltage or resistance values using a DVOM while attempting to reproduce conditions which will create an intermittent fault. A change in status on the DVOM will indicate a fault has been located.

When using a voltmeter to pinpoint faults, monitor voltage reading with ignition on, or vehicle running. A change in status on the voltmeter while performing intermittent TEST PROCEDURES will indicate area of fault.

When using an ohmmeter to detect problems in the circuit, monitor circuit resistance (ohms) with ignition switch in the OFF position, or with battery disconnected. A change in ohmmeter reading while performing TEST PROCEDURES will indicate area of fault.

INTERMITTENT SIMULATION

To reproduce the conditions which create an intermittent fault so that it may be identified during testing, some of the following methods may be used

  1. Applying light vibration to components.
  2. Heating a component.
  3. Wiggling or bending a wiring harness.
  4. Applying humidity to a component.
  5. Remove or apply a vacuum supply source.

Monitor circuit/component voltage or resistance while attempting to simulate intermittent. If vehicle is running, monitor for self-diagnostic codes. Use the results of these tests to identify a faulty component or an area which should be checked closely for the problem.

"SERVICE ENGINE SOON" light comes on but does not stay on. A stored code may or may not exist.

To track down possible causes of an intermittent "SERVICE ENGINE SOON" light check the following items

  1. Check for poor mating of one connector to another. Terminals may not be fully seated. Check for improperly formed or damaged terminals. Check wire to terminal connections.
  2. Check for poor connection from ignition coil to ground or arcing at spark plug wires or plugs.
  3. Check wire from "SERVICE ENGINE SOON" light to ECM for short to ground.
  4. Check wire from ALDL "test" terminal for intermittent short to ground.
  5. Check for poor connections in ECM ground terminals.
  6. Check for loss of trouble code memory. To check code memory on fuel injected models, disconnect TPS and run engine at idle until "SERVICE ENGINE SOON" light comes on. Code 22 should be stored and retained in memory when ignition is turned off. On carbureted engines, ground dwell lead for 10 seconds with ALDL "test" lead left ungrounded. Code 23 should be stored and retained in memory after ignition is turned off. If not, ECM is faulty.
  7. Check for electrical system interference caused by a defective relay or an ECM driven solenoid or switch which may cause a sharp electrical surge. This type of problem will normally occur when faulty component is operated.
  8. Check for aftermarket parts which may not have been produced to manufacturers' specifications. Solenoids without original equipment diodes for circuit protection and HEI-EST module or voltage regulator using transistors instead of silicon-chip circuitry may possibly cause voltage surges (up to 300 volts) in ECM wiring, causing temporary ECM shutdown. ECM shutdown is a normal response to system overvoltage (over 16 volts on most models). ECM will repower when condition ceases to exist. This could cause a flickering "SERVICE ENGINE SOON" light with no codes set in memory.
  9. Check for improper installation of electrical accessories such as auxiliary lights or 2-way radios.
  10. Make sure that EST wires are kept away from spark plug wires, distributor wires, distributor housing, ignition coil and generator. Make sure that ground wire from ECM to distributor or ignition module is connected to a good ground.
  11. Check for intermittent short to ground on terminal "B" (diagnostic enable) of ALDL or in "SERVICE ENGINE SOON" light circuit.
  12. On vehicles not equipped with a driver information center, check for intermittent wiring problem using "Scan" tester. See SCAN TESTER USAGE in the appropriate TESTS W/CODES article.

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