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Engine Controls - Tests W/o Codes - Efi: Other Isuzu Rodeo I

Testing & Diagnostics ~927 words

TERMINOLOGY

Due to Federal government requirements, manufacturers may use names and acronyms for systems and components different than those used in previous years. The following table will help eliminate confusion when dealing with these components and systems.

Former Name Or AcronymNew Name Or Acronym
ALDLData Link Connector (DLC)
CHECK ENGINE lightMalfunction Indicator Light (MIL)
ECMPowertrain Control Module (PCM)
Trouble CodesDiagnostic Trouble Codes DTC(s)

SAE TERMINOLOGY

DIFFICULT TO START

  1. Check for contaminated fuel.
  2. Check fuel pressure.
  3. Check for faulty Throttle Position (TP) Sensor.
  4. Check for faulty coolant temperature sensor.
  5. Check for loss of crank signal to PCM.
  6. Check EGR system.
  7. Check fuel pump relay and circuit.
  8. Check for faulty in-tank fuel pump check valve.
  9. Check ignition system.
  10. Check for faulty Idle Air Control (IAC) operation (if equipped).
  11. Check for incorrect EEPROM application (Stylus).
  12. Check for faulty main (or PCM) relay.

SURGES

  1. Check ignition system.
  2. Check PCM and ignition grounds.
  3. Check for contaminated fuel.
  4. Check for restricted fuel filter.
  5. Check fuel pressure.
  6. Check for injector leakage.
  7. Check for intermittent EGR at idle.
  8. Check for incorrect charging system voltage.
  9. Check for faulty PCV operation.
  10. Check for faulty Throttle Position (TP) Sensor.
  11. Check O2 sensor for silicone contamination from fuel or improper RTV sealant.
  12. Check for faulty MAP sensor.
  13. Check for faulty coolant temperature sensor.
  14. Use scan tester to ensure vehicle speed sensor reading matches actual vehicle speed.
  15. Check for faulty A/C operation.
  16. Check for faulty park/neutral switch.

LACK OF POWER

  1. Check ignition system.
  2. Check for faulty PCM or ignition grounds.
  3. Check ignition timing.
  4. Check for contaminated fuel.
  5. Check fuel pressure.
  6. Check for restricted fuel filter.
  7. Check EGR system.
  8. Check for restricted air filter.
  9. Check for faulty Throttle Position (TP) Sensor.
  10. Check for faulty MAP sensor.
  11. Check O2 sensor for silicone contamination from fuel or improper RTV sealant.
  12. Check for faulty coolant temperature sensor.
  13. Use scan tester to ensure vehicle speed sensor reading matches actual vehicle speed.
  14. Check A/C system operation.
  15. Check charging system voltage.
  16. Check power steering operation.
  17. Check for faulty automatic transmission/transaxle operation.
  18. Check valve timing.
  19. Check for improper or worn camshaft.
  20. Check engine compression.
  21. Check for restricted exhaust system.

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 knock sensor (if equipped) and circuit.
  4. Check for correct PROM or EEPROM.
  5. Check spark plugs for correct heat range.
  6. Check ignition timing.
  7. Check for low fuel pressure.
  8. Check EGR system operation.
  9. Check automatic transmission/transaxle for correct shift points.
  10. Check for carbon build-up in cylinders.

HESITATION, SAG OR STUMBLE

  1. Check fuel pressure.
  2. Check for contaminated fuel.
  3. Check for binding Throttle Position (TP) Sensor.
  4. Check ignition timing.
  5. Check MAP sensor (if equipped) operation.
  6. Ensure charging system voltage is correct.
  7. Ensure ignition system is properly grounded.
  8. Check for faulty spark plugs or wires.
  9. Check canister purge system.
  10. Check EGR system.

CUTS OUT OR MISSES

  1. Check ignition system.
  2. Check spark plugs.
  3. Check secondary ignition wires.
  4. Check for restricted fuel filter.
  5. Check for faulty injector(s).
  6. Check fuel pressure.
  7. Check for vacuum leaks.
  8. Check engine compression.
  9. Check valve timing.
  10. Check for damaged or worn push rods, rocker arms, valve springs and camshaft lobes.
  11. Check Throttle Position (TP) Sensor and circuit.

POOR FUEL MILEAGE

  1. Check fuel pressure.
  2. Check ignition timing.
  3. Check spark plugs.
  4. Check for correct tire pressure, vehicle carrying heavy loads or poor driving habits.
  5. Check if A/C is on all the time.
  6. Check for restricted air filter.
  7. Check for restricted exhaust system.
  8. Check for proper speedometer calibration.
  9. Check compression.
  10. Check for dragging brakes.
  11. Check gasoline quality.
  12. Check for cooling system running too hot or cold.

ROUGH OR UNSTABLE IDLE

  1. Check fuel pressure.
  2. Check ignition timing.
  3. Check for leaking fuel injector(s).
  4. Check for restricted air filter.
  5. Check Throttle Position (TP) Sensor operation.
  6. Check for open EGR valve at idle.
  7. Check PCV valve operation.
  8. Check O2 sensor for silicone contamination from fuel or improper RTV sealant.
  9. Check for fuel in fuel pressure regulator hose, indicating a faulty fuel pressure regulator.
  10. Check knock sensor operation (if equipped).
  11. Check for correct charging system voltage.
  12. Check canister purge system operation.
  13. Check Idle Air Control (IAC) system operation (if equipped).
  14. Check MAP sensor (if equipped) operation.
  15. Check for high A/C pressure due to overcharge or faulty pressure switch.
  16. Check power steering pressure switch and circuit operation.
  17. Ensure battery cables are clean and tight.
  18. Ensure engine compression is correct.

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. Check for improperly installed fuel filler cap.
  8. Check EGR valve operation.
  9. Check cooling system operation.

BACKFIRE

  1. Check ignition timing.
  2. Check ignition coil output.
  3. Check for faulty spark plugs.
  4. Check EGR system.
  5. Check for crossfire between spark plugs.
  6. Check for correct valve timing.

DIESELING (RUN-ON)

  1. Check for leaking injectors.
  2. Check for vacuum leaks.
  3. Check for carbon build-up in cylinders.
  4. Check for poor fuel quality.

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 (MIL)

  1. Check for electrical system interference from faulty relay, PCM- driven solenoid or switch. Faulty components can cause sharp electrical surge when operated.
  2. 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.
  3. Check for ignition secondary circuit shorted to ground. Check for shorted light circuit. Check for poor PCM grounds.

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