Circuit/System Testing
- Verify that none of the following conditions exist:
- Fuel contamination. Refer to Alcohol/Contaminants-in-Fuel Diagnosis (w/o Special Tool) or Alcohol/Contaminants-in-Fuel Diagnosis (w/Special tool) .
- Splits, kinks, or improper connections at the vacuum hoses.
- The fuel system is operating lean or rich. Refer to Fuel System Diagnosis .
- The fuel injectors are operating lean or rich. Refer to Fuel Injector Coil Test .
- Missing, restricted, or leaking exhaust components. Refer to Symptoms - Engine Exhaust in Engine Exhaust.
- Vacuum leaks at the intake manifold, throttle body, and injector O-rings - P0171.
- Leaking crankcase ventilation system - P0171.
- The air intake duct for being collapsed or restricted possibly by a restricted air filter - P0172.
- Leaking fuel pressure regulator. Inspect for evidence of fuel in the vacuum line-Refer to Fuel System Diagnosis - P0172.
- Excessive fuel in the crankcase - P0172.
- The incorrect operation of the evaporative emissions control system - P0172.
- If all conditions test normal, test the engine for a mechanical condition. Refer to Symptoms - Engine Mechanical .