GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Hesitation, Sag, Stumble

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

Preliminary
    • Refer to Important Preliminary Checks.
    • Refer to Visual/Physical Checks
    • Search for bulletins.

Sensor/System
    • Test the Heated Oxygen Sensor(s). The Heated Oxygen Sensors should quickly respond to different throttle positions. If not, inspect the HO2S for silicon or for other contaminants from the fuel or fro the use of an improper RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage, indicating a rich exhaust. The PCM will reduce the amount of fuel that is delivered to the engine, causing a severe driveability problem. Refer to Information Sensors/Switches Description - Heated Oxygen Sensors.
    • Test the TP Sensor and test the related wiring.
    • Test the MAF Sensor and test the related wiring.
    • Test the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .

Fuel System
    • Test the fuel pressure. Refer to Fuel System Pressure Test (VIN K) and refer to Fuel System Pressure Test (VIN 1) .
    • Test the fuel system for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis Alcohol-in-Fuel Diagnosis .
    • Test the fuel injectors using the following tests:
       -  Fuel Injector Balance Test
    • Inspect for conditions which can cause an engine to run rich, indicating that the long-term fuel trim is significantly in the negative range. Refer to DTC P0172 Fuel Trim System Rich .
    • Inspect for conditions that can cause an engine to run lean. indicating that the long-term fuel trim is significantly in the positive range. Refer to DTC P0171 Fuel Trim System Lean .

Ignition System
    • Test for proper ignition voltage output using the following steps:
        1. Clip the spark tester J 26792 to engine ground.
        2. Connect one end of a spark plug wire to the spark tester, and leave the other end of the spark plug wire to the coil that is being tested.
        3. Connect one end of another spark plug wire to the other coil tower, and connect the other end of the spark plug wire to ground.
        4. Crank the engine while you observe the spark tester. You should observe a spark.
        5. Repeat the above steps for each coil.
    • If no spark is present at the coils, check for the following conditions:
       - The coils--Check for cracks, for carbon tracking and arcing, or for a secondary resistance value that is outside the specified range.

Coil Resistance
5000-8000 ohms (5K- 8K ohms)

       - The spark plug wires--Inspect for signs of arcing or cross-firing, for cracks, for carbon tracking, for plug boot damage, for pinches, for improper routing, or for a resistance value that is outside the specified range.

Spark Plug Wire Resistance
600 ohms per ft.

   Important: Spraying the secondary ignition wires with a light mist of water may help to locate an intermittent problem. The ignition components will arc to ground when a secondary component is faulty.

       - A defective module
       - The ignition system wiring--Inspect for a loose ignition module feed or ground connection, or for damaged system wiring.
    • Remove the spark plugs and inspect for the following conditions:
       - Fouled plugs
       - Cracks
       - Wear
       - Improper gap
       - Burned or damaged electrodes
       - Improper heat range or reach
    • If the spark plugs are gas or oil fouled, determine the cause of the fouling before you replace the spark plugs.
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