GM Service Manual Online
For 1990-2009 cars only

Checks

Action

DEFINITION: Momentary lack of response as the accelerator is pushed down. Can occur at any vehicle speed. Usually more pronounced when first trying to make the vehicle move, as from a stop sign. May cause the engine to stall if severe enough.

Preliminary

    • Refer to Symptoms - Engine Controls , Important Preliminary Checks Before Starting.
    • Search for bulletins.
    • Verify that the powertrain control module (PCM) grounds are clean, tight, and in the correct locations.

Sensor and System

    • Check the manifold absolute pressure (MAP) sensor operation.
    • Check for a loose exhaust gas recirculation (EGR) and for a faulty gasket. Check for EGR flow all the time.
    • Using a scan tool, monitor the throttle position (TP) sensor voltage. The TP sensor voltage should be less than 0.9 volt at rest. Also inspect the throttle body and the accelerator cables for binding.

Fuel System

    • Check for a low fuel pressure. Refer to Cuts Out, Misses .
    • Check for a restricted fuel filter.
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check for open fuel injector fuses. Replace the fuse if necessary. Inspect the injector circuits for an intermittent short to ground.
    • Perform the fuel injector balance test.
    • Check the items that can cause an engine to run rich.
    • Check the items that can cause an engine to run lean.

Ignition System

Remove the spark plugs and check for the following conditions:

    • Any wet plugs
    • Any cracks
    • Any wear
    • An improper gap
    • Any burned electrodes
    • Any heavy deposits

An improper spark plug gap will cause a driveability problem. The spark plug gapping should be done with a wire gauge gap tool. If the spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

    • Check for a loose ignition control module ground.
    • Check the spark plugs for the correct heat range.
    •  Check for the correct ignition voltage output. Refer to Electronic Ignition (EI) System Diagnosis .

Engine Cooling System

Check the engine thermostat for correct operation and for the correct heat range. Refer to Engine Fails To Reach Normal Operating Temperature in Engine Cooling.

Additional Checks

Check the generator output voltage. Refer to Diagnostic Starting Point - Engine Electrical in Engine Electrical .