Cuts Out/Misses

Definition: Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases, not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or low speed.

PRELIMINARY CHECKS
^ Perform the careful visual/physical checks as described at start of"Symptoms".

ADDITIONAL CHECKS
^ CHECK: For EMI interference. A missing condition can be caused by Electromagnetic Interference (EMI) on the reference circuit. EMI can usually be detected by monitoring engine RPM with a Tech 1 scan tool. A sudden increase in RPM with little change in actual engine RPM change indicates EMI is present. If the problem exists, check routing of spark plug wires and electronic Ignition Control (IC) ground circuit.
^ CHECK: Intake and exhaust manifold passage for casting flash.

IGNITION SYSTEM

^ Check for cylinder miss:

1. Start engine allowing engine to stabilize then disconnect IAC valve. Remove one spark plug wire at a time using insulated pliers.

CAUTION: Do Not perform this test for more than 2 minutes, as this test may cause damage to the catalytic converter.

2. If there is an RPM drop on all cylinders (equal to within 50 RPM), go to "Rough, Unstable, or Incorrect Idle, Stalling"Rough, Unstable, or Incorrect Idle, Stalling symptom. Reconnect IAC valve.
3. If there is no RPM drop on one or more cylinders or excessive variation in RPM drop, check for spark on the suspected cylinder(s) using a shop oscilloscope or with J 26792 (ST-125) spark tester or equivalent. If no spark, refer to "Ignition System, Testing and Inspection" for intermittent operation or miss. If there is a spark, remove spark plug(s) in these cylinders and check for:

- Insulator cracks.
- Wear.
- Improper gap.
- Burned electrodes.
- Heavy deposits.

^ CHECK: Spark plug wires by connecting ohmmeter to ends of each wire in question. If meter reads over 30,000 ohms, replace wire(s).

ENGINE MECHANICAL
^ CHECK: Compression. Perform compression check on questionable cylinder(s) found above. If compression is low, repair as necessary.
^ CHECK: Base engine. Remove rocker covers. Check for bent pushrods, worn rocker arms, broken valve springs, worn camshaft lobes and valve timing. Repair as necessary.

FUEL SYSTEM
^ CHECK: Scan tool for injector fault which could indicate one or more faulty injectors or wiring.
^ CHECK: Fuel system - Plugged fuel filter, low pressure. Use CHART A-7.Related Tests, Information and Procedures
^ CHECK: Contaminated fuel.
^ CHECK: Injector drivers. Disconnect all injector harness connectors. Connect J 34730-2 injector test light or equivalent 6 volts test light between the harness terminals of each injector connector and note light while cranking. If test light fails to blink at any connector, it is a faulty injector drive circuit harness, connector or terminal or PCM.
^ CHECK: Perform the fuel injector coil/balance test. Refer to CHART C-2AChart C-2A Fuel Injector Balance Test.