GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1998 🢒 LeSabre 🢒 Engine 🢒 Engine Controls - 3.8L 🢒 Surges/Chuggles

Checks

Action

DEFINITION: Engine power variation under steady throttle or cruise. Feels like the vehicle speeds up and slows down with no change in the accelerator pedal.

Preliminary
    • Refer to Important Preliminary Checks.
    • Refer to Visual/Physical Checks
    • Be sure driver understands transmission torque converter clutch, and A/C compressor operation as explained in the owners manual. Inform customer how TCC and the A/C clutch operates.

Sensor/System
    • Check the Heated Oxygen Sensors. The Heated Oxygen Sensors should respond quickly to different throttle positions. If not, check 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 .
    • Check MAF Sensor and related wiring.
    • Check the EGR valve for a stuck open pintle.

Fuel System
    • Check the fuel pressure.
       - Refer to Fuel System Pressure Test (VIN K) .
       - Refer to Fuel System Pressure Test (VIN 1) .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Ensure each injector harness is connected to the correct injector/cylinder.
    • Check 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 .
    • Check 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 .

Ignition System
    • Check for proper ignition voltage output using the following steps:
       - Clip the spark tester J 26792 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 crisp blue spark should be observed.
       - Repeat the above steps for each coil.
    • If adequate spark is not present at the coils, check 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 greater than the specified value.

VIN 1 Spark Plug Wires Resistance
3280 - 4920 ohms per meter (1000 - 1500 ohms per foot).

VIN K Spark Plug Wires Resistance
3280 - 4920 ohms per meter (1000 - 1500 ohms per foot).

   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 check 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.

Additional Checks
    • Check TCC operation. Refer to Torque Converter Clutch Evaluation and Diagnosis .
    • Check the exhaust system for a possible restriction:
       - Inspect the exhaust system for damaged or collapsed pipes.
       - Inspect the muffler for heat distress or possible internal failure.
       - Check for possible plugged Three-Way catalytic converter. Refer to Restricted Exhaust System Check .