GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1997 🢒 Venture Ext. 🢒 Engine 🢒 Engine Controls - 3.4L (LA1) 🢒 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 Important Preliminary Checks .
    •  Refer to Visual/Physical Checks .
    •  Search for bulletins.

Fuel System Checks
    • Check the system fuel pressure. Refer to Fuel System Pressure Test .
    •  Check the fuel injectors. Refer to Fuel Injector Balance Test , Fuel Injector Solenoid Coil Test .
    •  Check for contaminated fuel. Refer to Alcohol/Contaminants-in-Fuel Test .
    •  Check items which can cause an engine to run rich (long term fuel trim is significantly in the negative range). Refer to DTC P0172 Fuel Trim System Rich .
    •  Check items that can cause an engine to run lean (long term fuel trim is significantly in the positive range). Refer to DTC P0171 Fuel Trim System Lean .

Sensor/System
    • Using a scan tool, monitor KS system for excessive spark retard activity. Refer to Knock Sensor (KS) System .
    •  Check the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System .
    •  Check for a restricted air intake system. Refer to Air Induction 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 - 7000ohms (5K - 7Kohms)

       -  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 Resistance
7000ohms (7Kohms)

    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 Restricted Exhaust System Check and Exhaust System.
    •  Check for proper TCC operation. Refer to Torque Converter Clutch in Transaxle Diagnosis.