GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2004 🢒 Park Avenue 🢒 Transmission/Transaxle 🢒 Automatic Transaxle - 4T65-E 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

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 in Symptoms - Engine Controls .
    • Refer to Visual/Physical Checks in Symptoms - Engine Controls .
    • Search for bulletins.

Fuel System Checks
    • Inspect the system fuel pressure. Refer to Fuel System Diagnosis .
    • Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect 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 P0171 .
    • Inspect 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 P0172 .

Sensor/System
    • Using a scan tool, inspect for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .
    • Inspect the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
    • Inspect for a restricted air intake system. Refer to Air Intake System Description .

Ignition System
    • Test for proper ignition voltage output using the following steps:
        1. Clip the J 26792 Spark Tester to engine ground.
        2. Connect one end of a spark plug wire to the spark tester. Leave the other end of the spark plug wire connected to the coil being tested.
        3. Connect another spark plug wire between the remaining tower of the coil being tested and ground.
        4. Crank the engine while observing the spark tester, a spark should be observed.
        5. Repeat the above steps for each coil.
    • If spark is not present at the coils, inspect for the following conditions:

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

       - Coils--Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

Coil Resistance
5,000-8,000 ohms

       - Spark plug wires--Signs of arcing/cross firing, cracks, carbon tracking, plug boot damage, pinched, improper routing, or a resistance value outside the specified range.

Spark Plug Wire Resistance-Regular
9,840 ohms per meter (3,000 ohms per foot)

Spark Plug Wire Resistance-Police
1,968 ohms per meter (600 ohms per foot)

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

       - Defective module
       - Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring.
    • Remove the spark plugs. Inspect for the following:
       - Fouled plugs
       - Cracks
       - Inspect the spark plugs for carbon tracking on the porcelain and pitting on the plug wire contact.
       - Improper gap
       - Burned or damaged electrodes
       - Improper heat range or reach
       - Refer to Maintenance Items in Maintenance and Lubrication.
    • If the spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to Spark Plug Inspection .

Engine Mechanical
    • Excess oil in combustion chamber--Inspect for leaking valve seals. Refer to Oil Leak Diagnosis in Engine Mechanical-3.8L.
    • Low cylinder compression. Refer to Engine Compression Test in Engine Mechanical-3.8L.
    • Inspect for incorrect engine parts, such as the following basic components:
       - Camshaft
       - Cylinder heads
       - Pistons etc.
    •  Refer to Engine Compression Test in Engine Mechanical-3.8L.

Additional Checks
    • Inspect the exhaust system for the following possible restrictions:
       - Inspect exhaust system for damaged or collapsed pipes.
       - Inspect mufflers for heat distress or possible internal failure.
       - For possible plugged three-way catalytic converter--Refer to Restricted Exhaust in Engine Exhaust .
    • Inspect for proper torque converter clutch (TCC) operation. Refer to Diagnostic Starting Point - Automatic Transmission in Automatic Transaxle-4T65-E.