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 Important Preliminary Checks.
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, for intermittent operation or miss, refer to Distributor Ignition System Check.

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.

ENGINE MECHANICAL
CHECK: Perform a cylinder compression check. If compression is low, repair as necessary.
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.

FUEL SYSTEM
CHECK: Fuel system - plugged fuel filter, low pressure. Refer to Chart A-6 Fuel System Diagnosis.
Related Tests, Information and Procedures
Contaminated fuel or restricted fuel filter.

ADDITIONAL CHECKS
CHECK: For Electromagnetic Interference (EMI). A missing condition can be caused by EMI on the reference circuit. EMI can usually be detected by monitoring engine RPM with a scan tool. A sudden increase in RPM with little change in actual engine RPM change, indicates EMI is present. If the problem exists, check routing of secondary wires, check ground circuit.