GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Venture Ext. 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 Lack of Power, Sluggishness, or Sponginess

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
    • Perform the Diagnostic System Check - Vehicle in Vehicle DTC Information.
    •  Refer to Intermittent Conditions before beginning.
    •  Search for bulletins.

Fuel System Test
    •  Test the fuel system 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
    • Test the crankshaft position (CKP) sensor B for an internal short. Refer to Electronic Ignition (EI) System Diagnosis .
    •  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, disconnect the KS, 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 powertrain control module (PCM). Refer to Powertrain Control Module Replacement .
    •  Inspect the exhaust gas recirculation (EGR) system for proper operation, if applicable.
    •  Inspect the air intake ducts for being collapsed, damaged areas, looseness, improper installation, or leaking especially between the mass air flow (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
5000-8000 ohms (5K-8K 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
9 686 ohms per meter (3,000 ohms per foot)

    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 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.