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
- Refer to Preliminary Checks. - Important Preliminary Checks
- If there is spray from only one injector on the TBI unit, there may be 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 Diagnostic Charts / Chart A-3. Testing and Inspection

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 test may cause damage to the catalytic converter.

2. If there is an RPM drop, on all cylinders, (equal to within 50 RPM), refer to Rough, Unstable or Incorrect Idle, Stalling. Rough, Unstable, or Incorrect Idle, Stalling
Reconnect IAC motor with 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.
4. If no spark, refer to Diagnostic Charts / C Charts / Distributor Ignition System Check. Testing and Inspection
5. If there is spark, remove spark plug(s) in these cylinders and check for:
- Insulation cracks.
- Wear.
- Improper gap.
- Burned electrodes.
- Heavy deposits.

Spark plug wire resistance (should not exceed 30,000 ohms), also, check rotor and distributor cap.

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-6 Fuel System Diagnosis.
Testing and Inspection
- For contaminated fuel or restricted fuel filter.

ENGINE MECHANICAL
CHECK:

- For proper valve timing, low compression, bent pushrods, worn rocker arms, broken or weak valve springs, worn camshaft lobes.
- Intake and exhaust manifold passage for casting flash.