Cuts Out/Misses

DEFINITION
Steady pulsation or jerking that follows engine speed, usually more pronounced as engine load increases, not normally felt above 1500 RPM or 48 km/h (30 mph). The exhaust has a steady spitting sound at idle or low speed.

PRELIMINARY CHECKS
Perform the careful visual / physical checks as described in Diagnosis By Symptom / Preliminary Checks.Testing and Inspection

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 Tech 1 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 spark plug wires and ignition control module ground circuit.
^ Check intake and exhaust manifold passage for casting flash.

IGNITION SYSTEM
^ Check for cylinder miss:

1. Start engine allowing engine to stabilize then disconnect Idle Air Control (IAC) motor. Remove one spark plug wire at a time using J 21350 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), go to Diagnosis By Symptom/ / ough, Unstable or Incorrect Idle, Stalling. Reconnect IAC valve. Rough, Unstable, or Incorrect Idle, Stalling

3. If there is no rpm drop on one or more cylinders or excessive variation in RPM drop, check for spark on the suspected cylinder(s) using a shop oscilloscope or with J 26792 (ST-125) spark tester or equivalent. If no spark refer to Ignition System for intermittent operation or miss. If there is a spark, remove spark plug(s) in these cylinders and check for:

- Insulator cracked or blistered (wrong heat range).
- 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).

ENGINE MECHANICAL
^ Check compression. Perform compression check on questionable cylinder(s) found above. If compression is low, repair as necessary.
^ Check base engine. Remove rocker covers. Check for bent pushrods, worn rocker arms, broken valve springs, worn camshaft lobes and valve timing. Repair as necessary.

FUEL SYSTEM
^ Check fuel system for Plugged fuel filter, low pressure. See Diagnostic Charts / A Charts / Chart A-7 Fuel System Diagnosis. Related Tests, Information and Procedures
^ Check for 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.
^ Perform the injector coil / balance test. Refer to Diagnostic Charts / C Charts / Chart C-2A Fuel Injector Test Procedure. Chart C-2A Fuel Injector Balance Test