Cuts Out/Misses

DEFINITION
Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases. The exhaust has a steady spitting sound at idle or low speed.

PRELIMINARY CHECKS
Perform the careful visual and physical checks as described in Preliminary Checks. Testing and Inspection

Fuel System Preliminary Checks
If there is spray from only one injector, then, there is a malfunction in the injector assembly, or in the signal to the injector assembly. The malfunction can be isolated by switching the injector connectors. If the problem remains with the original injector, after switching the connector, the injector is defective. Replace the injector. If the problem moves with the injector connector, the problem is an improper signal in the injector circuits. Refer to Chart A-3 Engine Cranks But Will Not Run. Related Tests, Information and Procedures

IGNITION SYSTEM
Check: For cylinder miss by:

1. Start engine, allow engine to stabilize then disconnect Idle Air Control (IAC) motor. Remove one ignition wire at a time, using insulated pliers.

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

2. If there is an RPM drop, on all cylinders, (equal to within 50 RPM), refer to the Rough, Unstable or Incorrect Idle, Stalling symptom. Reconnect IAC motor. Rough, Unstable, or Incorrect Idle, Stalling

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) with J26792 (ST-125) Spark Tester. If no spark, refer to Chart C-4 Distributor Ignition System Check. Chart C-4 Distributor Ignition (DI) System Check

If there is spark, remove spark plug(s) in these cylinders and check for:
^ Insulation Cracks
^ Wear
^ Improper Gap
^ Burned Electrodes
^ Heavy Deposits

Check: Ignition wire resistance (should not exceed 30,000 ohms), also, check rotor and distributor cap.

NOTE: If the previous checks did not find the problem:

^ Visually inspect ignition system for moisture, dust, cracks and burns. With engine running spray ignition wires with fine water mist to check for shorts.

FUEL SYSTEM
Check: Fuel pressure. Refer to Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures

Check: For contaminated fuel or restricted fuel filter.

ENGINE MECHANICAL
Check: For proper valve timing. Remove rocker covers. Check for bent pushrods, worn rocker arms, broken or weak valve springs, worn camshaft lobes. Repair as necessary.

Check: Low compression. Perform compression check.

Check: Intake and exhaust manifold passages for casting flash.