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

Checks

Action

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

Preliminary
    • Refer to the Symptoms .
    • Search for bulletins.

Sensor/System
    • Test the heated oxygen sensors. The heated oxygen sensors should respond quickly to different throttle positions. If not, inspect the HO2S for silicon or other contaminants from fuel or use of incorrect RTV sealant. The sensors may have a white powdery coating. Silicon contamination causes a high but false HO2S signal voltage (rich exhaust indication). The PCM will reduce the amount of fuel delivered to the engine, causing a severe driveability problem. Refer to heated oxygen sensors in Information Sensors/Switches Description .
    • Test the TP sensors and inspect the related wiring.
    • Test the MAF sensor and inspect the related wiring.
    • Test the EGR valve for a sticking pintle. Refer to Exhaust Gas Recirculation Valve Replacement .

Fuel System
    • Test the fuel pressure.
    • Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Test the injectors.
    • Test items which can cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to Diagnostic Aids for DTC P0172 Fuel Trim System Rich Bank 1 .
    • Test items that can cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to Diagnostic Aids for DTC P0171 Fuel Trim System Lean Bank 1 .

Ignition System
    • Test for proper ignition voltage output using the following steps:
       - Clip the J 26792 spark tester to engine ground.
       - Connect one end of a spark plug wire to the spark tester, leave the other end of the spark plug wire to the coil being tested.
       - Connect one end of another spark plug wire to the other coil tower, connect the other end of the spark plug wire to ground.
       - Crank the engine while observing the spark tester, a spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the coils, test for the following conditions:
       - Coils - Cracks, carbon tracking/arcing, or a resistance value outside the specified range.

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

       - Spark Plug wires - Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, incorrect routing, or a resistance value more than the specified value.

Spark Plug Wires Resistance
3280-4921 ohm/meter(1000-1500 ohm/ft).

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

       - Malfunctioning ignition control module.
       - Ignition System Wiring - Loose ignition module feed or ground connection, or damaged system wiring.
    • Remove spark plugs and inspect for the following conditions:
       - Fouled plugs
       - Cracks
       - Wear
       - Incorrect gap
       - Burned or damaged electrodes
       - Incorrect heat range
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.