GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Impala 🢒 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 .
    • Refer to Visual/Physical Checks in Symptoms .
    • Search for bulletins.

Fuel System Checks
    • Check the system fuel pressure. Refer to Fuel System Pressure Test (VIN K) .
    • Check the fuel injectors using the following procedures:
       -  Fuel Injector Balance Test
    • Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • 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 .

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

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 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 plug, check for the following conditions:
       - Coils- Cracks, carbon tracking/arcing, or a secondary resistance value outside the specified range.

Coil Resistance
5000-8000 ohms (5K-8K 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
600 ohms per/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 faulty.

       - Defective module
       - Ignition System Wiring - Loose ignition module feed or ground connection, or damaged system wiring.
    • Remove spark plugs and check for the following:
       - Fouled plugs
       - Cracks

   Important: If carbon tracking is detected on any component replace that component and it's mate. 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 Spark Plug Usage in Engine Electrical.
    • If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.

Engine Mechanical
    • Excessive oil in combustion chamber-Leaking valve seals.
    • Low cylinder compression
    • For incorrect basic engine parts. Inspect the following components:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.

Refer to Engine Compression Test .

Additional Checks

Check exhaust system for 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 System Check .
    • Check for proper TCC operation. Refer to Torque Converter Diagnosis in Automatic Transaxle.