Cuts Out/Misses

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 checks as described at start of "Symptoms".



IGNITION SYSTEM

^ CHECK: For cylinder miss by:

1. Start engine, allow engine to stabilize then disconnect IAC motor. Remove one spark plug 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), go to "Rough, Unstable Or Incorrect Idle, Stalling" symptom. Reconnect IAC motor with engine "OFF," ignition "OFF."

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 J 26792 (ST-125) Spark Tester or equivalent. If no spark, use CHART C-4. If there is spark, remove spark plug(s) in these cylinders and check for:

- Insulation Cracks.

- Wear.

- Improper Gap.

- Burned Electrodes.

- Heavy Deposits.

^ CHECK: Spark plug wire resistance (should not exceed 30,000 ohms), also, check ignition and connections.


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

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



FUEL SYSTEM

^ CHECK: Fuel Pressure, use CHART A-7.

^ CHECK: For contaminated fuel or restricted fuel filter.



ENGINE MECHANICAL

^ CHECK: For proper valve timing. Remove rocker covers. Check for, worn lifters, 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.