GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Grand Prix 🢒 Engine 🢒 Engine Controls - 3.1L (LG8) 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggish or Spongy

Inspection/Tests

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 Intermittent Conditions .
    •  Search for bulletins.

Fuel System Test
    •  Test the system fuel pressure. Refer to Fuel System Pressure Test .
    •  Inspect for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Diagnosis .
    •  Inspect any items which may cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to Diagnostic Aids for DTC P0172.
    •  Inspect any items that may cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to Diagnostic Aids for DTC P0171.

Sensor/System
    • Using a scan tool, monitor KS system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .
    •  If knock retard is above 10°-12°, disconnect the Knock Sensor, and ground the sensor harness connector. Monitor knock retard on the scan tool, there should be no knock retard present, if knock retard is still present, replace the PCM. Refer to Powertrain Control Module Replacement/Programming .
    •  Inspect the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
    •  Inspect MAF Sensor and related wiring.
    •  Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the MAF sensor and the throttle body.

Ignition System
    • Inspect for proper ignition voltage output using the following steps:
        1.  attach the J 26792 spark tester to engine ground.
        2.  Connect the spark plug end of the spark plug wire to the J 26792 spark tester; leave the other end of the spark plug wire connected to the coil being tested.
        3.  Connect the spark plug end of the companion spark plug wire to ground.

The companion spark plug wire is the wire attached to the corresponding coil tower.

        4.  Crank the engine while observing the J 26792 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:
       -  Coils--Cracks, carbon tracking/arcing, or a resistance value outside the specified range.

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

       -  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
600ohms per foot (1 968ohms per meter).

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

       -  Defective ignition module.
       -  Ignition system wiring--Loose ignition module feed or ground connection, or damaged system wiring.
    •  Remove spark plugs and inspect for the following conditions:
       -  Fouled plugs
       -  Cracks
       -  Wear
       -  Improper gap
       -  Burned or damaged electrodes
       -  Improper heat range or reach
    •  If spark plugs are gas or oil fouled, the cause of the fouling must be determined before replacing the spark plugs. Refer to Spark Plug Visual Diagnosis in Engine Electrical.

Engine Mechanical
    • Excessive oil in combustion chamber--Leaking valve seals. Refer to Base Engine Misfire Diagnosis in Engine Mechanical.
    •  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 in Engine Mechanical.

Additional

Inspect the 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 .
    •  Test for proper TCC operation. Refer to Torque Converter Diagnosis in Automatic Transaxle.