GM Service Manual Online
For 1990-2009 cars only

Checks

Action

DEFINITION: The engine has a power variation under a steady throttle or cruise. The vehicle seems to speed up and slow down without a change in pressure on the accelerator pedal.

Preliminary Checks

    • Refer to Symptoms - Engine Controls .
    • Be sure the driver understands the torque converter clutch (TCC) operation.
    • Be sure the driver understands the A/C compressor operation.
    • Use the scan tool in order to ensure the reading of vehicle speed sensor (VSS) matches the vehicle speedometer. This excludes vehicles with electronic transmissions where some variation between the VSS and the speedometer is normal.

Fuel System Checks

Check the fuel pressure while the condition exists. Refer to Fuel System Diagnosis .

Additional Checks

    • Check the control module grounds for being clean, tight, and in their proper locations.
    • Check the generator output voltage. Repair if less than 9 or more than 16 volts.
    • Check the vacuum lines for kinks or leaks.
    • Check the TCC operation.