GM Service Manual Online
For 1990-2009 cars only

Checks

Action

DEFINITION: A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with the throttle opening.

Preliminary Checks

    • Refer to Symptoms - Engine Controls .
    • Ensure the vehicle has an actual condition.
    • Inspect for smoke associated with the combustion noise.

Cooling System Checks

    • Inspect for obvious overheating conditions. Refer to Engine Overheating .
    • Inspect for a low engine coolant level.
    • Inspect for any restricted air flow through the radiator. Refer to Radiator Cleaning .
    • Inspect for a malfunctioning or incorrect thermostat.
    • Inspect for a correct coolant solution. The solution should be a 50/50 mix of anti-freeze and water.

Sensor Check

    • Inspect the engine coolant temperature (ECT) sensor by using the scan tool in order to compare the ECT with the ambient air temperature on a cold engine. If the coolant temperature reading is more than 5 degrees more or less than the ambient air temperature on a cold engine, inspect for a high resistance in the coolant sensor circuit or the sensor itself.
    • Inspect the fuel rail pressure (FRP) sensor. Use the scan tool to observe FRP with the engine OFF. FRP should be near 1.4 MPa. If not , inspect for high resistance in the low reference or 5-volt reference circuits or the sensor.
    • Inspect for an intermittent crankshaft position (CKP) sensor signal.

Fuel System Checks

    • If excessive smoke is present, inspect for a stuck open fuel injector.
        1. Disconnect all of the fuel injector electrical connectors.
        2. Remove the glow plugs.

        Important: DO NOT stand in front of the glow plug holes while cranking the engine.

        3. Crank the engine while observing the holes for fuel spray.
        4. Replace the fuel injectors for the cylinders that spray fuel.
        5. Inspect for fuel in the oil and proper oil level. Change the oil, as necessary.
    • Inspect for plugged fuel injectors.

Engine Mechanical Checks

    • Inspect for incorrect basic engine parts such as cam, heads, pistons, etc.
    • Inspect for any excessive oil entering combustion chamber.

Additional Checks

Review the Service Bulletins for control module software updates.