GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Grand Am 🢒 Engine 🢒 Engine Electrical 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

Tests/inspections

Action

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

Preliminary
    • Refer to Symptoms - Engine Controls .
    • Search for service bulletins.
    • Test and compare the customer's vehicle to a similar vehicle. Make sure the customer's vehicle has an actual problem.
    • Inspect the air cleaner filter for dirt and obstructions.

Fuel System
    • Test the fuel pressure. Refer to Fuel System Diagnosis .
    • Test for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    • Inspect the 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 .
    • Inspect the 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 .
    • Inspect the throttle linkage and throttle cables to ensure the throttle plate opens fully.

Sensor/System
    • Use a scan tool in order to observe the knock sensor (KS) system for excessive spark retard activity.
    • Test for correct operation of the manifold absolute pressure (MAP) sensor. Refer to DTC P0105 .
    • Test for correct operation of the throttle position (TP) sensor. Refer to DTC P0105 .
    • Test for correct operation of the oxygen sensor (O2S 1). Refer to DTC P0131 and DTC P0132 .
    • Inspect for a restricted air intake system.

Ignition System
    • Test for the correct ignition voltage output with the J 36012-A spark plug jumper wires and J 26792 spark tester or equivalent.
    • Inspect the spark plugs for the following conditions:
       - Any moisture or fuel fouling
       - Any cracks
       - An incorrect gap
       - Any burnt electrodes or heavy deposits
    • If the spark plugs are fuel or oil fouled, the cause of the fouling must be determined before replacing the spark plugs.
    • Inspect the ignition control module (ICM) for a correct ground connection.
    • Inspect the ignition coils for cracks or carbon tracking.

Engine Mechanical

Inspect the engine for the following mechanical problems:

    • A low compression. Refer to Engine Compression Test in Engine Mechanical.
    • A leaking cylinder head gasket. Refer to Engine Compression Test in Engine Mechanical.
    • A worn or an incorrect camshaft.

Additional
    • Test for the correct operation of the transaxle and the TCC. Refer to Road Test in Automatic Transaxle.
    • Inspect the exhaust system for the following conditions:
       - Any damaged or collapsed pipes.
       - Any heat distress or internal failure of the muffler.
       - A plugged 3-way catalytic converter. Refer to Restricted Exhaust in Engine Exhaust.
    • Inspect the vacuum lines for kinks or leaks.
    • Test the generator output voltage. Refer to Diagnostic System Check - Engine Electrical in Engine Electrical.
    • Test the A/C system operation. Refer to Symptoms - HVAC Systems - Manual in HVAC Systems. The A/C clutch should cut out at the wide open throttle (WOT) position.

If all procedures have been completed and no malfunctions have not been found, test and inspect all of the connections within the suspected circuit and systems.

Observe all of the scan tool data for the suspected circuit and systems.