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Engine Controls - Tests W/o Codes: Diagnosis Ford Bronco V

Testing & Diagnostics ~2615 words

SYMPTOMS

Symptom checks cannot be used properly unless problem occurs while vehicle is being tested. To reduce diagnostic time, ensure steps in F - BASIC TESTING article in the ENGINE PERFORMANCE section and TESTS W/CODES - EEC-IV article in the ENGINE PERFORMANCE section were performed before diagnosing a symptom.

Symptoms available for diagnosis are as follows

  1. No Crank
  2. Hard Start/Long Crank
  3. Stalls After Start
  4. No Start/Normal Crank
  5. Slow Return To Idle
  6. Rough Idle
  7. Low Idle (Stalls On Deceleration)
  8. Hesitates Or Stalls
  9. Surge (On Acceleration Or Cruise)
  10. Backfires
  11. Loss Of Power
  12. Spark Knock
  13. Poor Fuel Economy
  14. Emissions Compliance
  15. Warning Indicator Lights
  16. Improper Transmission Shift
  17. High Oil Consumption
  18. Engine Runs Hot (Overheating)
  19. Engine Runs Cold
  20. Exhaust Smoke
  21. Sulfur "Rotten Egg" Smell
  22. Engine Noise
  23. Vibration
  24. A/C System Not Functioning (Lack Of Cooling)
  25. A/C System Always On
  26. A/C Clutch Does Not Disengage Under WOT Conditions

Symptom Checks

Perform the following

  1. Check starter relay.
  2. Check starting system.
  3. Check charging system.
  4. Check for seized/hydro-static locked engine (leaking injectors).
  5. Check for defective flywheel or seized engine components.
  6. Check ignition circuit. In particular, check for ignition starter wire shorting to ground (distributor-equipped vehicles only).
  7. Check brake interlock switch (if equipped).
  8. Check transmission linkage adjustment.

Perform the following

  1. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  2. Check fuel system/throttle body. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check for restricted exhaust system.
  4. Check cooling system for overheating (hard hot start only). Also see ENGINE RUNS HOT (OVERHEATING).
  5. Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  6. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  7. Check starting system.
  8. Check Exhaust Gas Recirculation (EGR) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  9. Check for contaminated MAF sensor.

Perform the following

  1. Check for restricted exhaust system.
  2. Check for restricted air intake duct.
  3. Check EGR system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  4. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  5. Check idle speed. See IDLE SPEED in «ADJUSTMENTS»(ref-22969) article in the ENGINE PERFORMANCE section.
  6. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
  7. Ensure transmission is functioning properly.
  8. Perform CIRCUIT TEST S. See «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  9. If engine stalls during parking maneuvers, check Power Steering Pressure (PSP) switch operation. See step 3) of CIRCUIT TEST FF in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  10. If engine stalls during transmission engagement, check transmission solenoids. Go to CIRCUIT TEST TC in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  11. If engine stalls with A/C on, go to step 30) of CIRCUIT TEST KM in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.

Perform the following

  1. Check ignition system. On models with Distributor Ignition (DI) except Villager, perform CIRCUIT TEST AA. On 4.0L engine, perform CIRCUIT TEST AC. Proceed to «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  2. Check for restricted exhaust system.
  3. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.

Perform the following

  1. Check for throttle body contamination. Check for carbon build-up around throttle plate.
  2. Check air intake duct for leaks.

Perform the following

  1. Check RPM drop using step 2) of CIRCUIT TEST S, or power to MAP/BARO sensor using step 3) of CIRCUIT TEST S. See «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  2. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check idle speed. See IDLE SPEED in «ADJUSTMENTS»(ref-22969) article in the ENGINE PERFORMANCE section.
  4. Check fuel delivery and fuel pump. See FUEL SYSTEM in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  5. Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  6. Ensure engine operates at normal operating temperature.
  7. Check Exhaust Gas Recirculation (EGR) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  8. Check engine mechanical condition. Check compression, camshaft, valve train components, intake manifold gaskets, etc.
  9. Check air injection. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  10. Check air intake system. Ensure throttle plate and linkages operate properly.
  11. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  12. Check for restricted exhaust system.

Perform the following

  1. Check idle speed. See IDLE SPEED in «ADJUSTMENTS»(ref-22969) article in the ENGINE PERFORMANCE section.
  2. On A/T models with overdrive, check transmission solenoids. See CIRCUIT TEST TC in «G - TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  3. Check Exhaust Gas Recirculation (EGR) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  4. If low idle exists with A/C on, go to step 30) of CIRCUIT TEST KM in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.

Perform the following

  1. Check power to MAP/BARO sensor. See step 3) of CIRCUIT TEST S in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  2. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check idle speed. See IDLE SPEED in «ADJUSTMENTS»(ref-22969) article in the ENGINE PERFORMANCE section.
  4. Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  5. Ensure driveline and transmission are functioning properly.
  6. Check air intake system. Ensure throttle plate and linkages operate properly.
  7. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  8. Check for restricted exhaust system.
  9. Check EGR system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  10. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  11. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
  12. Check Heated Oxygen Sensor (HO2S) heater. Go to step 21) of CIRCUIT TEST H in «G - TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  13. Check cooling system (radiator, thermostat, etc.)
  14. Check customer driving habits (over RPM/speed limiting function enabled).

Perform the following

  1. Ensure engine is operating at normal operating temperature.
  2. Check power to MAP/BARO sensor. See step 3) of CIRCUIT TEST S in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  3. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  4. Check idle speed. See IDLE SPEED in «ADJUSTMENTS»(ref-22969) article in the ENGINE PERFORMANCE section.
  5. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  6. If surge occurs with A/C on, check A/C clutch operation. See appropriate AIR CONDITIONING & HEAT article in the ENGINE PERFORMANCE section.
  7. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  8. Check EGR system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  9. Check air injection (if equipped). See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  10. Check air intake system. Ensure throttle plate and linkages operate properly.
  11. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  12. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
  13. Check Heated Oxygen Sensor (HO2S). Go to step 21) of «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  14. Ensure speed (cruise) control system is functioning properly.

Perform the following

  1. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  2. Check air injection (if equipped). See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check engine mechanical condition. Check compression, intake manifold gasket, camshaft, valve train components, etc.
  4. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.

Perform the following

  1. Check power to MAP/BARO sensor. See step 3) of CIRCUIT TEST S in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  2. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  4. Check for restricted exhaust system.
  5. Ensure engine operates at normal operating temperature.
  6. Check air intake system. Ensure throttle plate and linkages operate properly.
  7. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
  8. Ensure transmission is functioning properly.
  9. Check for binding/dragging brakes.
  10. Ensure A/C turns off during Wide Open Throttle (WOT).
  11. Check customer driving habits.

Perform the following

  1. Check cooling system. If cooling system is overheating, go to ENGINE RUNS HOT (OVERHEATING) symptom.
  2. Check base timing. See DIAGNOSTIC SUB-ROUTINES.
  3. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
  4. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  5. Check Exhaust Gas Recirculation (EGR) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  6. Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  7. Check air injection. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  8. Ensure transmission is functioning properly.

Perform the following

  1. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  2. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check for restricted exhaust system.
  4. Ensure engine is operating at normal operating temperature.
  5. Check EGR system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  6. Ensure transmission is functioning properly.
  7. Check air injection (if equipped). See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  8. Check PCV system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  9. Check for binding/dragging brakes.
  10. Check engine mechanical condition. Check compression, camshaft, valve train components, etc.
  11. Check for contaminated Mass Airflow (MAF) sensor.

Perform the following

  1. Ensure engine operates at normal operating temperature.
  2. Check ignition system. See IGNITION SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  3. Check power to MAP/BARO sensor. See step 3) of CIRCUIT TEST S in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  4. Check idle speed. See IDLE SPEED in «ADJUSTMENTS»(ref-22969) article in the ENGINE PERFORMANCE section.
  5. Check PCV system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  6. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  7. Check air injection (if equipped). See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  8. Check EGR system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  9. Check engine mechanical condition. Check compression, intake manifold gasket, camshaft and valve train components, etc.

Perform the following

  1. Check if Malfunction Indicator Light (MIL) is on. Check instrument cluster as required.
  2. Check if 4x4 LOW or Transmission Control Indicator Light (TCIL) is on. Check instrument cluster as required.
  3. If MIL is never on, go to step 4) of CIRCUIT TEST ML in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  4. If MIL is on intermittently, go to step 10) of CIRCUIT TEST ML in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  5. If MIL is flashing (erratic idle), go to step 15) of CIRCUIT TEST ML in «G - TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  6. If 4x4 LOW indicator light is always off, go to step 4) of CIRCUIT TEST TB in «G - TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.

Perform the following

  1. Check wiring harness connectors.
  2. Check for vehicle modifications.
  3. Check for electronic add-on items.
  4. Check for misadjusted shift linkage.
  5. If transmission shifts early in 4x4 HIGH position, go to step 7) of CIRCUIT TEST TB in «G - TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.

Perform the following

  1. Check Positive Crankcase Ventilation (PCV) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  2. Check engine mechanical condition. Check valves, valve guides, valve stem oil seals, intake manifold gaskets, cylinder head oil drain passages and piston rings.

Perform the following

  1. If vehicle is equipped with electric cooling fan, Start engine. Turn A/C on (if equipped). Cooling fan should be on.
  2. Check ignition timing. See DIAGNOSTIC SUB-ROUTINES.
  3. Check temperature gauge and sending unit.
  4. Check for binding/dragging brakes.
  5. Check transmission for overheating.
  6. Check for excessive vehicle load.
  7. Check for internal cylinder block and cylinder head leaks.

Perform the following

  1. Check cooling system operation.
  2. Check temperature gauge and sending unit.

Perform the following

  1. Check fuel delivery system. See FUEL SYSTEM in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.
  2. Check Fuel Evaporation (EVAP) system. See EMISSION SYSTEMS & SUB-SYSTEMS in «I - SYSTEM/COMPONENT TESTS»(ref-22986) article in the ENGINE PERFORMANCE section.

Perform the following

  1. Check radiator cooling fan.
  2. Check belt-driven components.
  3. Check engine mounts.
  4. Check crankshaft vibration damper.
  5. Check transmission.
  6. Check tires and wheels.
  7. Check driveline components.

Perform the following

  1. Ensure A/C system (demand switch) is on. Check voltage at A/C clutch. Wait at least 10 seconds for normal on/off cycling.
  2. If voltage to A/C clutch does not exist, go to CIRCUIT TEST KM in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.
  3. If voltage to A/C clutch exists, connect A/C manifold gauge set, and perform A/C system functional test.

Note. For additional A/C system information, see appropriate AIR CONDITIONING & HEAT article in the ENGINE PERFORMANCE section.

Perform the following

  1. Ensure A/C system (demand switch) is off. Disconnect A/C clutch and start engine. Check voltage at A/C clutch. If voltage is less than 2 volts, check A/C compressor and A/C system for malfunction.
  2. If voltage is more than 2 volts, check if A/C compressor can be turned off with A/C demand switch. If A/C compressor turns off, connect A/C manifold gauge set, and perform A/C system functional test.

Perform the following

  1. If A/C system does not disengage at Wide Open Throttle (WOT), go to step 15) of CIRCUIT TEST KM in «TESTS W/CODES - EEC-IV»(ref-22952) article in the ENGINE PERFORMANCE section.

INTERMITTENT PROBLEM DIAGNOSIS

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

If problem vehicle does not produce fault codes, monitor voltage or resistance using a DVOM while attempting to reproduce conditions causing intermittent fault. A status change on DVOM indicates a fault has been located.

Use a DVOM to pinpoint faults. When monitoring voltage, ensure ignition switch is in ON position or engine is running. Ensure ignition switch is in OFF position or negative battery cable is disconnected when monitoring circuit resistance. Status changes on DVOM during test procedures indicate area of fault.

More articles — Engine Controls - Tests W/o Codes