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. 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

IGNITION SYSTEM
Check for cylinder miss by:
1. Start engine, allow engine to stabilize then disconnect Idle Air Control (IAC) motor. Remove one injector connector at a time, using insulated pliers. If Tech 1 is available, it may be used to short out the cylinders rather than disconnecting injector connectors.
2. If there is a RPM drop on all cylinders (equal to within 50 RPM), go to Rough, Unstable, or Incorrect Idle, Stalling. Reconnect IAC 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 3 26792 (ST 125) spark tester or equivalent. If no spark, refer to Chart C-4F in System Diagnosis/Diagnostic Charts/C Charts Ignition Misfire Check. Chart C-4 Ignition Misfire Check

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).
^ With engine running, spray coils and plug wires with fine water mist to check for shorts.

FUEL SYSTEM
Check:
^ Fuel system Plugged fuel filter. low pressure. Use Chart A-7 in System Diagnosis/Diagnostic Charts/A Charts/Chart A-7. Related Tests, Information and Procedures

^ Contaminated fuel.
^ 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, refer to Chart A-3 (Part 1 of 2) in System Diagnosis/Diagnostic Charts/A Charts/Chart A-3. Related Tests, Information and Procedures

^ Perform the injector balance test. Refer to Chart C-2A in System Diagnosis/Diagnostic Charts/C Charts/Chart C-2A. Chart C-2A Injector Coil Balance Test Procedure

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

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. A sudden increase in displayed RPM with little change in actual engine RPM indicates EMI is present. If the problem exists, check routing of secondary wires, check ignition control module ground circuit.
^ Intake and exhaust manifold passage for casting flash.
^ For an intermittent camshaft position sensor or crankshaft position sensor fault by monitoring "Cam/Crank Error" on the Tech 1 data list. "Cam/Crank Error" will increase to above 2 counts while the engine is running if a fault exists. Use Diagnostic Trouble Code (DTC) PO341 chart for diagnosis of a "Cam/Crank Error" fault.
^ For DTC P1568 or P1599 set. If so, vehicle may be operating in "Power Management" mode. Use DTC P1568 or P1599 chart for diagnosis.