Fuel System Checks

Check the following items:

1. Check the fuel injectors. See FUEL INJECTOR BALANCE TEST WITH SPECIAL TOOL and FUEL INJECTOR COIL TEST under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L ION article.
2. Check for incorrect fuel pressure. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
3. Check for a restricted fuel filter.
4. Check for a contaminated fuel condition. See ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS WITH SPECIAL TOOL or ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS WITHOUT SPECIAL TOOL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L ION article.
5. Check for the following conditions that may cause the engine to run rich:
   • 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 SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
   • A leaking fuel pressure regulator. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
   • Vacuum hoses that are split, kinked, or improperly connected.
   • An air intake duct that is collapsed or restricted.
   • A dirty or restricted air filter.
6. Check for the following conditions that may cause the engine to run lean:
   • Water intrusion in the HO2S connector.
   • An exhaust leak between the HO2S and the engine.
   • Vacuum leaks.
   • Incorrect fuel pressure. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
   • Restricted fuel injectors. See FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 2.2L ION article.
   • Fuel contamination. See ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS WITH SPECIAL TOOL or ALCOHOL/CONTAMINANTS-IN-FUEL DIAGNOSIS WITHOUT SPECIAL TOOL under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 2.2L ION article.
   • Vacuum hoses that are split, kinked, or improperly connected.