GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Corvette 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 Hesitation, Sag, Stumble

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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 .
    • 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 System Check - 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 Extended Travel Brake Switch Circuit .

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 four ignition coils and four injectors not to operate. Replace the fuse. Inspect the ignition coil circuits and the injector circuits for an intermittent short to ground.
    • Inspect the items which can cause an engine to run rich (long term fuel trim near -13%). For a rich condition, refer to DTC P0132 HO2S Circuit High Voltage Bank 1 Sensor 1 and DTC P0152 HO2S Circuit High Voltage Bank 2 Sensor 1 .
    • Inspect the items that can cause an engine to run lean (long term fuel trim near 23%). For a lean condition, refer to DTC P0131 HO2S Circuit Low Voltage Bank 1 Sensor 1 and DTC P0151 HO2S Circuit Low Voltage Bank 2 Sensor 1 .

Ignition System
    • Wet down the secondary ignition system with water from a spray bottle. Wetting down the secondary ignition system may help locate damaged or deteriorated components. Look/listen for arcing or misfiring as you apply water.
    • Test for proper ignition voltage output with spark tester J 26792 . Refer to Electronic Ignition (EI) System Diagnosis for the procedure.
    • Remove the spark plugs and inspect for the following:
       - Correct heat range; refer to Spark Plug Usage in Engine Electrical.
       - Wet plugs; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Cracks; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Wear; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Improper gap; refer to Spark Plug Replacement in Engine Electrical.
       - Burned electrodes; refer to Spark Plug Visual Diagnosis in Engine Electrical.
       - Heavy deposits; refer to Spark Plug Visual Diagnosis in Engine Electrical.
    • An improper spark plug gap causes a driveability concern. Gap the spark plugs using a wire gauge gap tool (J 41319). 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 Fuel Trim System Rich Bank 1 or DTC P0175 Fuel Trim System Rich Bank 2 for diagnosis of the rich condition. Refer to Spark Plug Visual Diagnosis in Engine Electrical 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 Check in Engine Electrical. Repair the charging system if the generator output voltage is less than 9 volts or more than 16 volts.