Possible Cause & Correction

Check the following items:

• Check for proper valve timing.
• Check for engine vacuum leaks and/or engine not tuned to specifications.
• Check for faulty air injection divert valve or check valve.
• Check for electric air switching valve or air divert valve not switching air pump discharge to air cleaner during engine starting or deceleration.
• Check engine for sticking or leaking valves.
• Check for fuel or water in vacuum hose to MAP sensor. Also check for restricted hose.
• Using Spark Tester (ST-125), check available output voltage of ignition coil.
• Check for crossfire between spark plugs, distributor cap and spark plug wires.
• Check for an intermittent ignition system problem.
• Make sure that initial ignition timing is properly set.