Sensor/System Checks
- Check the following that may cause the engine to run rich:
- Any water intrusion in the HO2S connector.
- Engine oil contaminated by fuel.
- An EVAP canister purge condition.
- Incorrect fuel pressure. See FUEL SYSTEM DIAGNOSIS
under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
- A leaking fuel pressure regulator. See FUEL SYSTEM DIAGNOSIS
under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
- Leaking fuel injectors. See FUEL SYSTEM DIAGNOSIS
under FUEL SYSTEM in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
- Split, kinked, or improperly connected vacuum hoses.
- Collapsed or restricted air intake duct.
- Dirty or restricted air filter.
- Check the air intake system and crankcase for air leaks.
- Check for an Engine Coolant Temperature (ECT) sensor that has shifted in value. See TEMPERATURE VS. RESISTANCE
table.
- Check for an inaccurate speedometer.
- Monitor the Knock Sensor (KS) system for excessive spark retard activity with a scan tool.