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 as described at start of Section B.

^ Misses At Idle:

1. With engine idling, disconnect IAC motor. Remove one spark plug wire at a time using insulated pliers.

2. If there is an RPM drop on all cylinders, go to ROUGH, UNSTABLE, OR INCORRECT IDLE, OR STALLING symptom. Reconnect IAC motor.
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 spark exists:

Inspect plugs for:

- Cracks, Wear, Improper Gap

- Burned Electrodes, or Heave Deposits

- Perform compression check on questionable cylinder.

If no spark on suspected cylinders:

ON DISTRIBUTOR TYPE SYSTEM

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

ON NON-DISTRIBUTOR SYSTEMS

Ground the opposite plug wire of the effected coil pair. If tester now sparks replace the spark plug of the wire which was jumpered to ground. If tester still does not spark, refer to appropriate ignition chart in Section C4.

^ Cuts Out Under Load:

Test for spark on each wire with an J-26792 spark tester or equivalent. If there is spark on all cylinders, remove plugs and check for:

- Cracks, Wear, Improper Gap

- Burned Electrodes, or Heavy Deposits

If no spark at plug(s):

ON DISTRIBUTOR TYPE SYSTEM

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

ON NON-DISTRIBUTOR SYSTEMS

Ground the opposite plug wire of the effected coil pair. If tester now sparks replace the spark plug of the wire which was jumpered to ground. If tester still does not spark, refer to appropriate ignition chart in Section C4.
^ If above checks did not correct problem, check the following:

- Disconnect all injector harness connectors. Connect J-34730-2 Injector Test Light or equivalent 6 volt test light between the harness terminals 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.

- Perform the Injector Balance Test. See CHART C-2A.

- Visually inspect distributor cap and rotor for moisture, dust, cracks, burns, etc. Spray cap and plug wires with fine water mist to check for shorts.

- Fuel System - Plugged fuel filter, water, low pressure. See CHART A-7.

- Valve Timing

- Remove rocker covers. Check for bent pushrods, worn rocker arms, broken valve springs, worn camshaft lobes. Repair as necessary. See Section 6A.

- Perform compression check.

- On C3I systems, a misfire may be caused by a misaligned crank sensor or bent vane on rotating disc. Inspect for proper clearance at each vane, approximately .030" (.76 mm). Sensor should be replaced if it shows evidence of rubbing.