Possible Cause & Correction

Check the following items:

• Check for obvious overheating problems.
• Ensure initial timing is correct.
• Check TPS adjustment and operation.
• Check fuel system for low pressure or volume. Also check for induction air leaks.
• Ensure ESC system is operating properly.
• Ensure EGR valve is operating properly.
• Ensure TCC or VCC system is operating properly.
• Remove carbon from engine with top engine cleaner.
• If excessive carbon exists in combustion chamber, check for excessive oil burning due to leaking valve guide seals.
• Check for incorrect basic engine parts such as camshaft, cylinder heads and pistons.
• Ensure PROM/MEM-CAL in vehicle is correct for particular vehicle. Check with dealer for latest application information.
• Check coolant sensor for shift in calibration. Refer to the SENSOR RANGE CHARTS article (for all except Saturn) in this section. Sensor Range charts for Saturn are not available.
• Check for rich or lean running conditions.
• Check spark plugs for proper application and heat range.
• Check engine compression.
• Check P/N switch circuit. Ensure P/N switch is properly adjusted.
• Check for contaminated or poor quality fuel. Check vehicle operation using a higher octane fuel.