GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Corvette 🢒 Engine 🢒 Engine Electrical 🢒 Hesitation, Sag, Stumble

Checks

Action

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

Preliminary
    • Refer to Important Preliminary Inspections Before Starting in Symptoms - Engine Controls .
    • Search for bulletins.
    • Inspect the PCM grounds for being clean, tight, and in the proper locations. Refer to Engine Controls Schematics .

Sensor/System
    • Test the operation of the Column Lock System. Refer to Diagnostic Starting Point - Body Control System in Body Control System.
    • Test the MAP sensor operation.
    • An extended travel brake switch that is mis-adjusted or an extended travel brake circuit that is open causes a perceived misfire under heavy load conditions from a stop. Use a scan tool in order to monitor the extended travel brake switch parameter. If the scan tool displays extended travel brake switch applied when the brake pedal is released, refer to DTC P1575 .

Fuel System
    • Test for proper fuel pressure. Refer to Fuel System Diagnosis .
    • Inspect for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Inspect for a contaminated fuel condition. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    •  Inspect both injector fuses for being open. An open injector fuse causes 4  ignition coils and 4 injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground.
    • Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Inspect the items which can cause an engine to run rich having the long term fuel trim near -13 percent. For a rich condition, refer to DTC P0131 or P0151 and DTC P0132 or P0152 .
    • Inspect the items that can cause an engine to run lean, having the long term fuel trim near 23 percent. For a lean condition, refer to DTC P0131 or P0151 and DTC P0132 or P0152 .

Ignition System
    • Wet the secondary ignition system with water from a spray bottle. Wetting the secondary ignition system may help to locate damaged or deteriorated components. Look and listen for arcing or misfiring as you apply water.
    • Test for proper ignition voltage output withJ 26792 Spark Tester. Refer to Electronic Ignition (EI) System Diagnosis .
    • Remove the spark plugs and inspect for the following conditions:
       - Correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
    • To properly inspect the spark plugs or to correct a condition, refer to the following procedures:
       -  Spark Plug Inspection
       -  Spark Plug Replacement
    • An improper spark plug gap causes a driveability concern. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement .
    • Determine the cause of the fouling before replacing the spark plugs if the spark plugs are gas, coolant, or oil fouled. Refer to DTC P0172 or P0175 for diagnosis of the rich condition. Refer to Spark Plug Inspection for diagnosis of coolant or oil fouled spark plugs.
    • Inspect for loose ignition coil grounds. Refer to Electronic Ignition (EI) System Diagnosis .

Engine Cooling System

Test the engine thermostat for proper operation and correct heat range. Refer to Thermostat Diagnosis in Engine Cooling.

Additional Checks

Test the generator output voltage. Refer to Charging System Test in Engine Electrical. Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.