GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1999 🢒 Century 🢒 Engine 🢒 Engine Controls - 3.1L 🢒 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 Intermittent Conditions .
    •  Search for bulletins.

Fuel System Checks
    • Check the system fuel pressure. Refer to Fuel System Pressure 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.
    •  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.

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, if knock retard is still present, replace the PCM. Refer to Powertrain Control Module Replacement/Programming .
    •  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 J 26792 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 J 26792 Spark Tester; a spark should be observed.
       -  Repeat the above steps for each coil.
    •  If spark is not present at the coil(s), check for the following conditions:
       -  Coil(s)--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 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
       -  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.

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

Additional Checks

Check exhaust system for possible restrictions. Check for the following:

    •  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 Manifold Absolute Pressure Sensor Circuit Diagnosis and Exhaust System.
    •  Check for proper TCC operation. Refer to Torque Converter Diagnosis .