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 kph (30 mph). The exhaust has a steady spitting sound at idle or low speed.

Preliminary Checks
^ Perform the visual/physical checks as described under Diagnostic Notes in this section.

Ignition System
^ Check for cylinder miss by:

1. Start engine, allow engine to stabilize. 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 three-way catalytic converter (TWC) or the warm up three-way catalytic converter (WU-TWC).

2. If there is an rpm drop on all cylinders (equal to within 50 rpm), go to "Rough, Unstable, or Incorrect Idle, Stalling" symptom.

3. If there is no rpm drop on one or more cylinders, or excessive variation in drop. check for spark on the suspected cylinder(s) using a J26792 spark tester or equivalent. If no spark, check distributor components, secondary wiring and spark plug to determine cause and repair. 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 digital multimeter to ends of each wire in question. If meter reads over 25,000 ohms, replace wire(s).

^ CHECK: Distributor cap and rotor for moisture, dust, cracks, burns, etc. With engine running, spray cap and plug wires with fine water mist to check for shorts.

Fuel System
^ CHECK: Fuel system - plugged fuel filter.

^ CHECK: Contaminated fuel.

^ CHECK: Injector drivers. Disconnect all injector harness connectors. Connect a J34730-2B Injector Test Light between the harness terminal 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 faulty ECM/PCM.

Engine Mechanical
^ CHECK: Compression. Perform compression check on questionable cylinder(s) found in Ignition System checks. If compression is low, repair as necessary.

^ CHECK: Ease engine. Remove cam covers. Check for broken valve springs, worn camshaft lobes and valve timing. Repair as necessary.

Additional Checks
^ CHECK: Intake and exhaust manifold passage for casting flash.