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Engine Controls - Trouble Shooting - No Codes: Other Isuzu Rodeo II

Testing & Diagnostics ~2024 words

DIFFICULT TO START

Note. If engine cranks but will not start, see BASIC DIAGNOSTIC PROCEDURES article for trouble shooting procedure.

Check fuel pump relay by connecting test light between fuel pump relay connector ignition feed circuit and ground. Turn ignition on. Light should illuminate for 2 seconds. If light does not illuminate for 2 seconds, see FUEL PUMP RELAY under FUEL SYSTEM in SYSTEM & COMPONENT TESTING article. For location of fuel pump test connector, see COMPONENT LOCATIONS in SYSTEM & COMPONENT TESTING article.

  1. Check for blown injector fuse.
  2. Check for contaminated fuel.
  3. Check fuel pressure.
  4. Visually inspect injector fuse(s).
  5. Check for faulty Engine Coolant Temperature (ECT) sensor and circuit.
  6. Check Electronic Throttle Control (ETC) system operation.
  7. Check for faulty Intake Air Temperature (IAT) sensor and compare readings with ECT sensor.
  8. Check for loss of crank signal to PCM.
  9. Check EGR system.
  10. Check fuel pump relay and circuit.
  11. Check ignition system and grounds.
  12. Check for shorts by spraying plug wires with a fine mist of water.
  13. Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits.
  14. Check for faulty Idle Air Control (IAC) operation (if equipped).
  15. Check for faulty main (or PCM) relay.
  16. Check for faulty Throttle Position (TP) sensor.
  17. Check for faulty PCV system.
  18. Check for faulty Camshaft Position (CMP) sensor.
  19. Check Manifold Absolute Pressure (MAP) or Mass Air Flow (MAF) sensor.
  20. Check for faulty fuel pump relay.
  21. Check for faulty in-tank fuel pump check valve (if equipped). A faulty in-tank fuel pump check valve will allow fuel to drain back to tank after engine is stopped. To check this condition, turn ignition off, disconnect fuel pressure line at fuel rail and remove filler cap. Using a radiator test pump, apply 15 psi (1.0 kg/cm 2 ) pressure. If pressure holds for 60 seconds, check valve is okay.
  22. Ensure the installed PROM and/or PCM is correct for that particular vehicle. Check with dealer for latest application information.
  23. Check for improper or worn camshaft.
  24. Check engine compression.
  25. Check for leaking cylinder head gasket.
  26. Check fuel injectors drain down time and circuit.
  27. Check for intake and exhaust manifold leaks.

SURGES OR CHUGGLES

  1. Check ignition system and grounds.
  2. Check PCM and ignition grounds.
  3. Check for intermittent open or short to ground in Torque Converter Clutch (TCC) circuit.
  4. Check canister purge system for proper operation.
  5. Check for contaminated fuel.
  6. Check for restricted fuel filter.
  7. Check fuel pressure.
  8. 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.
  9. Check for injector leakage and connections.
  10. Check for intermittent EGR at idle.
  11. Check Electronic Throttle Control (ETC) system operation.
  12. Check for incorrect charging system voltage.
  13. Check for faulty PCV operation.
  14. Check for faulty throttle position sensor.
  15. Check oxygen sensor for silicone contamination from fuel or improper RTV sealant.
  16. Check for faulty Manifold Absolute Pressure (MAP) sensor.
  17. Check for faulty coolant temperature sensor.
  18. Use scan tester to ensure vehicle speed sensor reading matches actual vehicle speed.
  19. Check for rich or lean conditions. Drive vehicle at speed when complaint occurs.
  20. Check for faulty A/C operation.
  21. Check for faulty Park/Neutral Position (PNP) switch.
  22. Check Mass Air Flow (MAF) sensor connections.
  23. Check vacuum line condition and connections.
  24. Check generator output voltage.
  25. Check for excessive use of additives in fuel.
  26. Check restricted exhaust system.
  27. Check Heated Oxygen Sensor (HO2S).
  1. Check restricted air filter
  2. Check ignition system.
  3. Check for faulty PCM and grounds.
  4. Check ignition timing.
  5. Check Knock Sensor (KS) system for excessive retard.
  6. Check for faulty Torque Converter Clutch (TCC).
  7. Check for contaminated fuel.
  8. Check fuel pressure.
  9. Check for restricted fuel filter.
  10. Check EGR system.
  11. Check for restricted air filter.
  12. Check for faulty throttle position sensor.
  13. Check for faulty Manifold Absolute Pressure (MAP) sensor.
  14. Check oxygen sensor for silicone contamination from fuel or improper RTV sealant.
  15. Ensure the installed PROM and/or PCM is correct for that particular vehicle. Check with dealer for latest application information.
  16. Check for faulty Engine Coolant Temperature (ECT) sensor.
  17. Use scan tester to ensure vehicle speed sensor reading matches actual vehicle speed.
  18. Check A/C system operation.
  19. Check charging system voltage.
  20. Check power steering operation.
  21. Check for faulty automatic transmission operation.
  22. Check valve timing.
  23. Check for excessive fuel additives.
  24. Check for improper or worn camshaft.
  25. Check engine compression.
  26. Check for restricted exhaust system.
  27. Check Electronic Throttle Control (ETC) system operation.
  28. Check Variable Intake Manifold (VIM) solenoid valve.
  29. Check for faulty or restricted throttle body.
  30. Check for sticking or slaking throttle cable.

SPARK KNOCK/DETONATION

  1. Check for engine running hot because of low coolant or other cooling system faults.
  2. Check for correct fuel octane rating.
  3. Check engine compression.
  4. Check TP sensor adjustment and operation.
  5. Check Knock Sensor (KS) and circuit (if equipped).
  6. Check for correct PROM or EEPROM.
  7. Check spark plugs for correct heat range.
  8. Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
  9. Check ION sensing module operation.
  10. Check ignition timing.
  11. Check for low fuel pressure.
  12. Check EGR system operation.
  13. Check automatic Transmission Range (TR) switch circuit.
  14. Check for carbon build-up in cylinders.
  15. Check for correct fuel pressure.
  16. Check for rich or lean running conditions.
  17. Check for faulty Torque Converter Clutch (TCC).
  18. Check for faulty Engine Coolant Temperature (ECT) sensor.
  19. Check for restricted airflow to radiator.

HESITATION, SAG OR STUMBLE

Note. On some automatic transmissions hesitation may occur when first put in gear, after vehicle has not been running for a prolonged period of time. This is do to torque converter drain. For correction of symptom, refer to appropriate article in AUTOMATIC TRANSMISSIONS.

  1. Check for faulty Heated Oxygen Sensor (HO2S).
  2. Check fuel pressure.
  3. Check for contaminated fuel.
  4. Check for binding Throttle Position (TP) sensor.
  5. Check ignition timing.
  6. Ensure the installed PROM and/or PCM is correct for that particular vehicle. Check with dealer for latest application information.
  7. Check Manifold Absolute Pressure (MAP) sensor operation (if equipped).
  8. Ensure charging system voltage is correct.
  9. Ensure ignition system is properly grounded.
  10. Ensure PCM-controlled idle speed is correct.
  11. Check for faulty spark plugs or wires.
  12. Check canister purge system.
  13. Check EGR system.
  14. Check for faulty TP sensor.
  15. Check fuel injectors. Perform INJECTOR BALANCE TEST in SYSTEM & COMPONENT TESTING article.
  16. Check injector harness locations. Ensure injectors are connected to correct injector/cylinder according to firing order.
  17. Check for proper PCM grounding.
  18. Check for faulty Mass Air Flow (MAF) sensor connections.
  19. Check air induction system for restrictions.
  20. Check for intake valve deposits.
  21. Check for faulty vacuum lines.

CUTS OUT OR MISSES

  1. Check ignition system and grounds.
  2. Check spark plugs.
  3. Check secondary ignition wires.
  4. Ensure ignition control wiring harness is not routed too close to wiring which may cause induced voltage signals.
  5. Check ignition coil connections.
  6. Check for restricted fuel filter.
  7. Check for faulty injector(s) and connections.
  8. Check fuel pressure.
  9. Check for vacuum leaks.
  10. Check engine compression.
  11. Check valve timing.
  12. Check for damaged or worn push rods, rocker arms, valve springs and camshaft lobes.
  13. Check Throttle Position (TP) sensor and circuit.
  14. Check for faulty PCV system.
  15. Check for EGR valve sticking open.
  16. Check for proper Crankshaft Position (CKP) sensor resistance.
  17. Check for proper idle speed.
  18. Check for sticking or leaking valves.
  19. Check for faulty motor mounds.
  20. Check for faulty PCM grounds.
  21. Check for throttle body tampering.
  22. Check for faulty Idle Air Control (IAC) and throttle bore restrictions.
  23. Check for restricted air flow.
  24. Check for restricted exhaust system.
  25. Check for faulty Transmission Range (TR) switch circuit.
  26. Check for faulty Manifold Absolute Pressure (MAP) sensor and circuit.
  27. Ensure presence of a brake switch signal.
  28. Check idle speed.
  29. Check for contaminated fuel.

POOR FUEL MILEAGE

  1. Check fuel pressure.
  2. Check vacuum hoses.
  3. Check ignition timing.
  4. Check spark plugs.
  5. Check for correct tire pressure, vehicle carrying heavy loads or poor driving habits.
  6. Check if A/C is on all the time.
  7. Check for restricted air filter.
  8. Check for restricted exhaust system.
  9. Check for proper speedometer calibration.
  10. Check EGR system.
  11. Check oxygen sensor for silicone or lead contamination.
  12. Check engine compression.
  13. Check for dragging brakes.
  14. Check gasoline quality.
  15. Check for cooling system running too hot or cold.
  16. Check for faulty thermostat.
  17. Check for faulty Torque Converter Clutch (TCC).
  18. Check for leaks is air intake system and crankcase.

STALLING, ROUGH, UNSTABLE OR INCORRECT IDLE

  1. Check fuel pressure.
  2. Check throttle linkage and/or Throttle Position (TP) sensor for sticking or binding. Ensure throttle bore is free of foreign material.
  3. Check ignition timing.
  4. Check for leaking fuel injector(s) and connections.
  5. Check for restricted air filter.
  6. Check for open EGR valve at idle.
  7. Check PCV valve operation.
  8. Check for vacuum leaks.
  9. Check HO2S for silicone contamination from fuel or improper RTV sealant.
  10. Check for fuel in fuel pressure regulator hose, indicating a faulty fuel pressure regulator.
  11. Check for excessive fuel additives.
  12. Check Knock Sensor (KS) operation (if equipped).
  13. Ensure the installed PROM and/or PCM is correct for that particular vehicle. Check with dealer for latest application information.
  14. Check Engine Coolant Temperature (ECT) sensor for proper temperature-to-resistance values.
  15. Check for correct charging system voltage.
  16. Check canister purge system operation.
  17. Check Idle Air Control (IAC) system operation (if equipped).
  18. Check Manifold Absolute Pressure (MAP) sensor (if equipped) operation.
  19. Check for high A/C pressure due to overcharge or faulty pressure switch.
  20. Check power steering pressure switch and circuit operation.
  21. Ensure battery cables are clean and tight.
  22. Ensure engine compression is correct.
  23. Check for throttle body tampering.
  24. Check for restrictions in air intake.
  25. Check for faulty TP sensor and circuit.
  26. Check for faulty Transmission Range (TR) switch and circuit.
  27. Check for improper PCM grounds.
  28. Check ignition system and grounds.
  29. Check valve timing.
  30. Check for improper or worn camshaft.
  31. Check engine compression.
  32. Check for damaged or worn push rods, rocker arms, valve springs and camshaft lobes.
  33. Check for sticking or leaking valves.
  34. Check for faulty motor mounts.

EXCESSIVE EXHAUST EMISSIONS OR ODORS

  1. Check fuel pressure.
  2. Check ignition timing.
  3. Check charcoal canister for fuel saturation.
  4. Check PCV system operation.
  5. Check for faulty spark plugs.
  6. Check for lead contamination of catalytic converter.
  7. Ensure the installed PROM is correct for that particular vehicle. Check with dealer for latest application information.
  8. Check for improperly installed fuel filler cap.
  9. Check EGR valve operation.
  10. Check cooling system operation.
  11. Check cooling fan for proper operation.
  12. Check for vacuum leaks.
  13. Check for faulty fuel injectors and connections.
  14. Check for carbon build-up in cylinders.
  15. Check for engine mechanical problems.
  16. Check for use of excessive fuel additives.
  17. Check for excessive exhaust emissions.

BACKFIRE

  1. Check ignition timing.
  2. Check ignition coil output.
  3. Check for engine vacuum leaks and/or engine not tuned to specifications.
  4. Check secondary air injection system.
  5. Check for faulty spark plugs.
  6. Check EGR system.
  7. Check for fuel or water in vacuum hose to Manifold Absolute Pressure (MAP) sensor. Also check for restricted hose.
  8. Check fuel injectors. Perform INJECTOR BALANCE TEST in SYSTEM & COMPONENT TESTING article.
  9. Check for crossfire between spark plugs.
  10. Check for sticking or leaking valves.
  11. Check for improper or worn camshaft.
  12. Check engine compression.
  13. Check fuel pressure.
  14. Check for correct valve timing.
  15. Check harmonic balancer interrupter rings for missing, broken or bent vanes.
  16. Check for cracks in exhaust and intake manifold.

DIESELING (RUN-ON)

  1. Check for leaking injectors.
  2. Check for binding throttle linkage.
  3. Check for vacuum leaks.
  4. Check for carbon build-up in cylinders.
  5. Check for poor fuel quality.
  6. Check ignition timing.
  7. Check engine RPM.
  8. Check engine for overheating.
  9. Check for excessive use of fuel additives.
  10. Check for shorts between positive battery terminal and all ignition feed circuits.

Intermittent Simulation

To reproduce the conditions creating an intermittent fault, use the following methods

  1. Lightly vibrate component.
  2. Heat component.
  3. Wiggle or bend wiring harness.
  4. Spray component with water.
  5. Remove/apply vacuum source. Monitor circuit/component voltage or resistance while simulating intermittent. If engine is running, monitor for self-diagnostic codes. Use test results to identify a faulty component or circuit.

INTERMITTENT MALFUNCTION INDICATOR LIGHT

Check for electrical system interference from faulty relay, ECM-driven solenoid or switch. Faulty components can cause sharp electrical surge when operated.

  1. Check for incorrect installation of electrical options (2-way radios, cellular phones, etc.). Ensure EST ignition wiring is routed away from spark plug wiring. Ensure distributor is properly grounded.
  2. Check for ignition secondary circuit shorted to ground. Check for shorted Malfunction Indicator Light (MIL) circuit. Check for poor ECM grounds.

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