Cuts Out, Misses

DEFINITION
Steady pulsation or jerking that follows Engine speed, usually more pronounced as Engine load increases, not normally felt above 1500 revolution per minute (rpm) or 48 kph (30 mile per hour). The exhaust has a steady spitting sound at idle or low speed.

PRELIMINARY CHECKS
Perform the careful Visual/Physical Checks as described in Preliminary Checks.
Preliminary Checks

IGNITION SYSTEM
CHECK: For Cylinder Miss By:
1. Starting Engine, allow Engine to stabilize then disconnect Idle Air Control Motor. Remove one Spark Plug Wire at a time, using insulated pliers.

CAUTION:
Do not perform this test for more than 2 minutes, as it may cause damage to the Three Way Catalytic Converter.

2. If there is an rpm drop on all cylinders (equal to within 50 rpm), go to Diagnosis by Symptom / Rough, Unstable, or Incorrect Idle, Stalling. Rough, Unstable, or Incorrect Idle, Stalling

Reconnect Idle Air Control Valve.

3. If there is no rpm drop on one or more cylinders, or excessive variation is drop, check for spark on the suspected cylinder(s) using a shop oscilloscope or with J-26792 (ST-125) Spark Tester or equivalent.

4. If there is a spark, remove spark plug(s) in these cylinders and check for:
- Insulator Cracks.
- Wear.
- Improper Gap.
- Burned Electrodes.
- Heavy Deposits.

CHECK: Spark Plug Wires by connecting Ohmmeter to ends of each wire in question. If meter reads over 30,000 ohms, replace wire(s).

FUEL SYSTEM
CHECK: Fuel System For:
Plugged Fuel Filter or low pressure.
See Diagnostic Charts / Chart A-7.
A-7: Fuel System Diagnosis

CHECK: Contaminated Fuel.

CHECK: Injector Drivers. Disconnect all Injector Harness Connectors. Connect J-34730-2 Injector Test Light or equivalent 6 volts Test Light between the Harness Terminal, 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.

ENGINE MECHANICAL
CHECK: Compression. Perform compression check on questionable Cylinder(s) found above. If compression is low, repair as necessary.

CHECK: Engine parts. Remove Cam Covers. Check for broken Valve Springs, worn Camshaft Lobes and Valve timing.

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 speed with a Scan Tool. A sudden increase in rpm with little change in actual Engine speed change, indicates EMI is present. If the problem exists, check routing of secondary wires, check Distributor ground circuit.

CHECK: Intake and Exhaust Manifold passage for casting flash.