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.

Perform careful visual (physical) check.
If Ignition System is suspected of causing a miss at idle or cutting out underload, check for missing cylinder by:

1. Start engine. Disconnect IAC valve. Remove one spark plug wire at a time using insulated pliers.
2. If there is an rpm drop on all cylinders, (equal to within 50 rpm), go to ROUGH, UNSTABLE, OR INCORRECT IDLE, symptom. Stop Engine. Reconnect IAC valve.
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). If there is spark, remove spark plug(s) in these cylinders and check for:
- Cracks
- Wear
- Improper Gap
- Burned Electrodes
- Heavy Deposits
Check spark plug wire resistance (should not exceed 30,000 ohms).

Remove air cleaner and visually check fuel spray from injectors. 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 connectors, then the injector is defective. Replace the injector. If the problem moves with the injector connector, then, the problem is an improper signal in the injector circuits.

If the previous checks did not find the problem:
- Visually inspect distributor cap for moisture, dust, cracks, burns, etc. Spray plug wires and distributor cap with fine water mist to check for shorts or arcing.
- Fuel System - Plugged fuel filter, water, low pressure.
- Use "Scan" tool and check for erratic TPS voltage.
- Check Injector harness connectors for intermittent connections.
- Perform compression check, compression should not vary by more than 20% highest to lowest.
- Remove head covers. Check for broken or weak valve springs, worn camshaft lobes. Repair as necessary.