GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 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 - 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
    • Inspect for excessive spark retard activity with a scan tool. 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:
       - 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 connected to the coil being tested.
       - Connect another spark plug wire between the remaining tower of the coil being tested and 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, 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.
    • Low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    • Inspect for incorrect engine parts, such as the following basic components:
       - Camshaft
       - Cylinder heads
       - Pistons etc.
    •  Refer to Engine Compression Test in Engine Mechanical.

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.