GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T65-E 🢒 Lack of Power, Sluggishness, or Sponginess

Checks

Action

DEFINITION: Engine delivers less than expected power. Little or no increase in speed when the accelerator pedal is pushed down part way.

Preliminary Checks
    • Refer to Important Preliminary Checks Before Starting in Symptoms .
    • Refer to Visual/Physical Checks in Symptoms .
    • Search for bulletins.

Fuel System
    • Check the fuel pressure.
       - Refer to Fuel System Pressure Test (VIN K) .
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Check items which can cause an engine to run rich. Refer to DTC P0172 Fuel Trim System Rich .
    • Check items that can cause an engine to run lean. Refer to DTC P0171 Fuel Trim System Lean .

Sensor/System
    • Monitor the knock sensor system for excessive spark retard activity using a scan tool. Refer to Knock Sensor (KS) System Description .
    • Check the EGR valve for a stuck open pintle. Refer to Exhaust Gas Recirculation Valve Replacement .
    • Check for a restricted intake duct or a dirty air cleaner element. Refer to Air Cleaner Element Replacement .

Ignition System
    • Check 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 J 26792 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 J 26792 spark tester. A spark should be observed.
       - Repeat the above steps for each coil.
    • If spark is not present at the plugs, check for the following conditions:

   Important: If carbon tracking is detected on a component, replace that component and the component's mate.

       - Inspect the coils for cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

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

       - Inspect the spark plug wires for 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
1000 to 1500 ohms/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.

       - Check for a malfunctioning ignition control module.
       - Check the ignition system wiring for a loose ignition module feed, ground connection, or damaged system wiring.
    • Remove the spark plugs.
    • Inspect the spark plugs for the following conditions:

   Important: If carbon tracking is detected on a component, replace that component and the component's mate.

       - Check the spark plugs for carbon tracking on the porcelain and pitting on the plug wire contact.
       - Check the spark plugs for fouling.
       - Check the spark plugs for cracks.
       - Check the spark plugs for incorrect gap.
       - Check the spark plugs for burned or damaged electrodes.
       - Check the spark plugs for incorrect heat range. Refer to Maintenance Items .
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

Engine Mechanical
    • Check for excessive oil in combustion chamber or leaking valve seals. Refer to Oil Consumption Diagnosis
    • Inspect for low cylinder compression. Refer to Engine Compression Test
    • For incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    •  Refer to Base Engine Misfire Diagnosis .

Additional Checks
    • Check the exhaust system for a possible restriction.
       - Inspect the exhaust system for damaged or collapsed pipes.
       - Inspect the muffler for heat distress or an internal failure.
       - Check for a plugged three-way catalytic converter. Refer to Restricted Exhaust System Check .
    • Check for the proper TCC operation. Refer to Diagnostic Starting Point - Automatic Transmission .