Diagnostic Aids
Fuel-contaminated engine oil may set some codes and affect engine performance. If oil contamination is suspected, remove PCV valve from valve cover, and repeat QUICK TEST. If problem is corrected, change engine oil.
Vacuum leaks in non-EEC related areas may cause Code 41 or 91 to be displayed. Check vacuum motors, engine seals, EGR system, PCV system, Canister Purge (CANP), HEGO sensor and between airflow meter and throttle body for unmetered air leaks. Code 42 or 92 may be caused by fuel-contaminated engine oil, ignition misfire, or EGR system or CANP problems.