GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1999 🢒 Venture Ext. 🢒 Engine 🢒 Engine Controls - 3.4L 🢒 Lack of Power, Sluggishness, or Sponginess

Lack of Power, Sluggishness, or Sponginess x

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 connector. Monitor Knock Retard on the Scan Tool, there should be no retard present (if Knock Retard is present, replace the PCM) 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.

Ignition System
    • Check for proper ignition voltage output using the following steps:
       -  Clip the spark tester J 26792 to engine ground.
       -  Connect one end of a spark plug wire to the 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 spark tester; a crisp blue spark should be observed.
       -  Repeat the above steps for each coil.
    •  If adequate 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 - 7000 ohms (5K - 7K 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
7000 ohms (7K ohms)

    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 Engine Mechanical.
    •  Low cylinder compression. Refer to Engine Mechanical.
    •  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 Clutch in Transaxle Diagnosis.