GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 Engine 🢒 Engine Controls - 5.7L 🢒 Hesitation, Sag, Stumble

Checks

Action

DEFINITION: A momentary lack of response when the accelerator is pushed down. The condition can occur at any vehicle speed. The condition is usually more pronounced when the driver first attempts to make the vehicle move, as from a stop. If the condition is severe enough, the engine may stall.

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

Sensor/System

Test the MAP sensor operation.

Fuel System
    • Test for incorrect fuel pressure. Refer to Fuel System Diagnosis .
    • Test for a restricted fuel filter. Refer to Fuel System Diagnosis .
    • Test 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 to not operate. Replace the fuse. Inspect the ignition coil circuits. Iinspect the injector circuits for an intermittent short to ground.
    • Test the fuel injectors. Refer to Fuel Injector Solenoid Coil Test .
    • Inspect the items that cause an engine to run rich, with a long term fuel trim near -13 percent. For a rich condition, refer to DTC P0132 or P0152 .
    • Inspect the items that can cause an engine to run lean, with a long term fuel trim near 24 percent. For a lean condition, refer to DTC P0131 or P0151 .

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. When you apply the water, look and listen for arcing or misfiring.
    • 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:
       - The correct heat range
       - Wet plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned electrodes
       - Heavy deposits
       - Refer to Spark Plug Inspection in Engine Electrical.
    • An improper spark plug gap causes a driveability condition. Gap the spark plugs using a wire gauge gap tool. Refer to Spark Plug Replacement in Engine Electrical.
    • Before you replace the spark plugs, determine the cause of the fouling.
       - Gas fouling--Refer to DTC P0172 or P0175 .
       - Oil fouling--Refer to Oil Consumption Diagnosis in Engine Mechanical-5.7L.
       - Coolant fouling--Refer to Loss of Coolant in Engine Cooling.

Engine Cooling System

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

Additional Checks

Test the generator output voltage. Refer to Diagnostic Starting Point - Engine Electrical in Engine Electrical for the procedure. If the generator output voltage is less than 9 volts or more than 16 volts, repair the charging system.