Possible Causes & Corrections

Check the following items:

• Ensure EGR valve is not stuck open.
• Check for engine vacuum leaks. Ensure engine is tuned to specifications.
• Using Spark Tester (J-26792), check available output voltage of ignition coil.
• Check air induction system for restrictions or air leaks.
• Check exhaust system for restrictions, such as a damaged or collapsed pipe, muffler or catalytic converter. See EXHAUST SYSTEM BACKPRESSURE under MECHANICAL INSPECTION in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check fuel injectors. Perform injector balance test. See FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article.
• Check fuel system for incorrect fuel pressure. See BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
• Check engine compression. Check for incorrect valve timing, bent push rods, broken valve springs or worn camshaft lobes.
• Check transmission shift solenoid system and Torque Converter Clutch (TCC) system for proper operation.
• Check for intermittent ignition system problem.
• Check intake and exhaust manifold passages for casting flash.
• Remove spark plugs and check for wet plugs, cracks, improper gap, burned electrodes or heavy carbon deposits. Also, check condition of spark plug wires. Spray spark plug wires with a fine mist of water to check for shorts.
• Ensure initial ignition timing is properly set.
• Ensure speedometer is properly calibrated.