GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 1997 🢒 Venture Ext. 🢒 Engine 🢒 Engine Controls - 3.4L (LA1) 🢒 Cuts Out, Misses

Checks

Action

Definition: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases.

Preliminary
    • Refer to Important Preliminary Checks .
    •  Refer to Visual/Physical Checks
    •  Search for bulletins.

Fuel System
    • Check 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 Testing.
    •  Check items which can cause an engine to run rich (long term fuel trim 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 significantly in the positive range). Refer to DTC P0171 Fuel Trim System Lean .
    •  Check for fuel in the Fuel Pressure Regulator vacuum hose.

Sensor/System
  1. Check for conditions which cause an incorrect idle speed.
    2. • Throttle body tampering, excessive deposits, or damage. Refer to Fuel Metering System Components .
    •  Restricted air intake system. Refer to Air Induction System .
    •  Large vacuum leak.
  2. Check the TP Sensor and related circuit wiring. Refer to DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage .
  3. Check the EGR system for proper operation. Refer to Exhaust Gas Recirculation (EGR) System .
  4. Check the PCV Valve for proper operation. Refer to Crankcase Ventilation System .
  5. Check the Transaxle Range Switch input with the vehicle in drive and the gear selector in drive or overdrive. Refer to Transaxle Range Switch Valid Combinations.
  6. Check the following for damage:
    7. • Bent harmonic balancer interrupter rings.
    •  Damaged Crankshaft Position Sensor.

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 Wire 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.
    •  Check for the following intermittent ignition system conditions:
       -  Intermittent CKP 24X Signal.
       -  Intermittent ignition feed circuit or sensor ground circuit to the crankshaft position sensor or the camshaft position sensor.
       -  Intermittent 3X reference signal.
       -  Intermittent camshaft position signal

Engine Mechanical
    • Check engine mechanical for the following:
       - Check compression.
       - Sticking or leaking valves.
       - Worn camshaft lobe(s).
       - Valve timing.
       - Bent push rods.
       - Worn rocker arms.
       - Broken valve springs.
       - Excessive oil in combustion chamber-Leaking valve seals.
       - Low cylinder compression.
    • For incorrect basic engine parts. Inspect the following:
       - Camshaft
       - Cylinder heads
       - Pistons, etc.
    • Refer to Engine Mechanical for diagnosis procedures.

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.
    •  An engine miss condition can be caused by Electromagnetic Interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If a problem exists, check routing of secondary ignition wires, high voltage components (Near Ignition Control circuits).
    •  Check for intake and exhaust manifold passages for casting flash. Refer to Engine Mechanical.
    •  Check for faulty motor mounts. Refer to Engine Mechanical. .