GM Service Manual Online
For 1990-2009 cars only

Checks

Action

DEFINITION: The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur at any vehicle speed. The condition is usually most severe when trying to make the vehicle move from a stop. If sever enough, the condition may cause the engine to stall.

Preliminary Check

    • Refer to Symptoms - Engine Controls .
    • Remove the air filter and inspect for dirt, or for air ducts being plugged or restricted.
    • Inspect for proper transmission shift pattern and down shift operation.
    • Inspect the fuel quality.
    • Inspect the engine oil level and quality.

Fuel System Checks

    • Check the fuel pressure to the fuel injection pump. Fuel is under suction. If the pressure drops, a restriction exists in the fuel supply lines between the pump and the fuel tank.
    • Inspect for water contamination in the fuel. Refer to Contamination Testing .
    • Perform the cylinder balance test.
    • Inspect for high fuel supply system vacuum after a cold start or during moderate or full throttle acceleration. If the vacuum jumps above specification, there is a possible restriction in the fuel system.

Engine Mechanical Checks

Inspect the engine for the following conditions:

    • Low compression
    • Improper valve timing
    • Improper or worn camshaft

Sensor Checks

Inspect for an intermittent crankshaft position (CKP) sensor signal.

Additional Checks

    • Review the service bulletins for control module software updates.
    • Inspect the generator output voltage.