GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2001 🢒 Century 🢒 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 before starting.
    •  Search for bulletins.

Fuel System Test
    •  Test the fuel pump circuits for proper operation. Refer to Fuel Pump Electrical Circuit Diagnosis .
    •  Test for low fuel pressure. Refer to Fuel System Diagnosis .
    •  Test for faulty fuel injectors. Refer to Fuel Injector Balance Test with Special Tool , Fuel Injector Balance Test with Tech 2 , Fuel Injector Solenoid Coil Test test procedures.
    •  Inspect for fuel contamination. 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 which 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 knock sensor (KS) system for excessive spark retard activity. Refer to Knock Sensor (KS) System Description .
    •  If knock retard is above 10-12 degrees, refer to DTC P0327 .
    •  Inspect the exhaust gas recirculation (EGR) system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System Description .
    •  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 . 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 . 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 connected to proper spark plugs.

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:
       - Proper spark plugs
       -  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 Inspection .

Engine Mechanical
    •  Excessive oil in combustion chamber--Leaking valve seals. Refer to Oil Consumption Diagnosis in Engine Mechanical.
    •  Low cylinder compression. Refer to Engine Compression Test in Engine Mechanical.
    •  For incorrect basic engine parts. Inspect the following conditions:
       -  Cylinder heads
       -  Camshaft and valve train components
       -  Pistons, etc.

Additional

Inspect the exhaust system for any possible restrictions:

    •  Inspect exhaust system for damaged or collapsed pipes.
    •  Inspect mufflers for heat distress or possible internal failure.
    •  For possible plugged catalytic converter
    •  Test for proper torque converter clutch (TCC) operation. Refer to Torque Converter Diagnosis in Automatic Transaxle.