Fuel and Emissions Systems Symptom Troubleshooting

When the vehicle has one of these symptoms, check for a diagnostic trouble code (DTC) with the HDS. If there is no DTC, do the diagnostic procedure for the symptom, in the sequence listed, until you find the cause.

Symptom | Diagnostic procedure | Also check for
--- | --- | ---
Engine will not start (MIL works OK, no DTCs set) | 1. 2. 3. | Test the battery. Test the starter. Bleed the fuel system. |

- Low compression
- Intake air leaks
- Locked up engine
- Broken cam chain
- Contaminated fuel

Engine will not start (MIL comes on and stays on, or never comes on at all, no DTCs set) | Troubleshoot the MIL circuit. |
Engine will not start (immobilizer indicator stays on or flashes) | Troubleshoot the immobilizer system. |
Engine is hard to start (MIL works OK, no DTCs set) | 1. 2. | Test the battery. Bleed the fuel system. |

- Low compression
- Intake air leaks
- Contaminated fuel

Cold fast idle too low (MIL works OK, no DTCs set) | 1. 2. | Check the idle speed. Bleed the fuel system. |
Cold fast idle too high (MIL works OK, no DTCs set) | 1. 2. | Check the idle speed. Inspect/adjust the throttle cable. |
Idle speed fluctuates (MIL works OK, no DTCs set) | 1. 2. 3. | Check the idle speed. Inspect/adjust the throttle cable. Bleed the fuel system. | Intake vacuum leaks
After warming up, idle speed is above specifications without load (MIL works OK, no DTCs set) | Inspect/adjust the throttle cable. |
Idle speed fluctuates (MIL works OK, no DTCs set) | Bleed the fuel system. | Contaminated fuel
Fails emission test (MIL works OK, no DTCs set) | Inspect the catalytic converter. |

- Contaminated fuel
- Low compression
- Slipped/broken timing belt

Low power (MIL works OK, no DTCs set) | 1. 2. 3. | Check the air cleaner element. Inspect/adjust the throttle cable. Inspect the catalytic converter. |

- Contaminated fuel
- Low compression
- Camshaft timing
- Engine oil level

Engine stalls (MIL works OK, no DTCs set) | 1. 2. | Bleed the fuel system. Check the idle speed. |

- Intake air leaks
- Faulty harness and sensor connections