GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1997 🢒 Savana 🢒 Engine 🢒 Engine Controls - 5.0L, 5.7L, and 7.4L 🢒 Cuts Out, Misses

Checks

Action

Definition: A steady or jerking that follows engine speed, usually more pronounced as the engine load increases which is not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle, low speed, or hard acceleration for the fuel starvation that can cause the engine to cut-out.

Preliminary Check

Refer to Important Preliminary Checks .

Ignition System Checks
    • Check for a cylinder misfire:
    • On 5.7L (L31) and 7.4L (L29) engines, confirm that the distributor is adjusted so that CMP Retard is 0° ±2°. If it is not, refer to the "Distributor Adjustment Procedure". A misadjusted distributor can cause crossfire which would result in misfire.
  1. Start the engine.
  2. Allow the engine to stabilize.
  3. Then disconnect the Idle Air Control (IAC) motor.

    4. Notice: Do not perform this test for more than 2 minutes in order to prevent damaging the catalytic converter.

  4. Remove one spark plug wire at a time using insulated pliers.
  5. If there is a RPM drop on all cylinders (equal to within 50 RPM), go to Rough, Unstable, or Incorrect Idle and Stalling .
  6. Reconnect the IAC motor with the ignition OFF.
  7. If there is no RPM drop on one or more of the cylinders, or excessive variation in drop, check for spark on the suspected cylinders with a J 26792 or the equivalent.
  8. If there is no spark, refer to Enhanced Ignition System .
  9. If there is spark, remove the spark plugs in these cylinders and check for the following conditions:
    10. • Insulation cracks
    • Wear
    • Improper gap
    • Burned electrodes
    • Heavy deposits
       - Check the spark plug wire resistance (should not exceed 30,000 ohms).
       - Check the distributor rotor and the distributor cap.
       - If the previous check did not find the problem, visually check the following items:
    • The ignition system for moisture, dust, cracks, burns, etc.
    • With the engine running, spray the plug wires with a fine water mist to check for shorts.

Engine Mechanical Checks
    • Perform a cylinder compression check. Refer to Engine Mechanical.
    • Check the engine for the following:
       - Improper valve timing
       - Bent pushrods,
       - Worn rocker arms
       - Worn camshaft lobes
       - Broken or weak valve springs Refer to Engine Mechanical.
    • Check the intake and exhaust manifold passages for casting flash. Refer to Engine Mechanical.

Fuel System Checks
    • Check the fuel system - plugged fuel filter, low fuel pressure, etc. Refer to Fuel System Diagnosis .
    • Check for water contamination in the fuel.
    • Check the fuel injector driver circuit.
    • Perform the fuel injector coil test. Refer to Fuel Injector Solenoid Coil Test .
    • Perform the fuel injector balance test. Refer to Fuel Injector Balance Test .

Additional Check
    • Check for Electromagnetic Interference (EMI).
    • The EMI on the reference circuit can cause a missing condition.
    • Monitoring the engine RPM with a scan tool can detect an EMI.
    • A sudden increase in the RPM with little change in the actual engine RPM, indicates EMI is present.
    • If the problem exists, check the routing of the secondary wires and the ground circuit.