GM Service Manual Online
For 1990-2009 cars only

Checks

Action

DEFINITION: The fuel ignites in the intake manifold, or in the exhaust system, making a loud popping noise.

Preliminary Check

    • Refer to Symptoms .

Ignition System Checks

    • Check for adequate ignition coil voltage with a J 26792 spark tester or equivalent.
    • Check the spark plugs for any of the following conditions:
       - Wet (fuel fouled) plugs.
       - A terminal screw that is bent or loose (rotate and pull).
       - A ceramic insulator that has cracks, carbon tracking or deposits (red or black dust)
       - A tip insulator that has cracks, carbon tracking, deposits (oil, carbon, glazing, fuel additive), or is loose (rattles).
       - A center electrode that is loose (wiggles side to side)
       - An incorrect spark plug gap that is too large or too small.
    • Check for crossfiring between spark plugs (faulty spark plug wires or improper routing of plug wires).

Engine Mechanical Checks

    • Check for any of the following engine mechanical problems:
       - Incorrect valve lash
       - Broken or weak valve springs
       - Low compression
       - Sticking or leaking valves
       - Incorrect valve timing
       - Incorrect or worn camshaft
    • Refer to Engine Mechanical.
    • Check the intake and exhaust system for casting flash or other restrictions.

Additional Checks

    • Check for the proper fuel pressure. Refer to Fuel System Diagnosis .
    • Check the PCM grounds for being clean, tight, and in their proper locations. Refer to PCM Power and Ground electrical schematic.
    • Check the Service Bulletins for any updates or information.