DEFINITION: The engine runs unevenly at idle. If bad enough, the vehicle may shake. Also, the idle may vary in RPM (called hunting). Either condition may be bad enough to cause stalling. Engine idles at incorrect speed.

Misfire Counts

Check misfire counts using a scan tool (if any exist)

Throttle Linkage

Check throttle linkage for sticking or binding

Throttle Position Sensor

Check throttle position sensor, should read 0% at idle on a scan tool.

Idle Air Control (IAC) Valve

Check for a carboned-up IAC valve .

Generator charging output voltage

Repair if less than 13 volts or more than 16 volts with engine running and all accessories OFF.

Injectors

Check for clogged injectors. Perform Injector Balance test.

Evaporative Emissions (EVAP) solenoid

Check for EVAP purge solenoid stuck open.

Catalytic Converter

Check for Catalytic converter blockage.

Engine Mounts

Broken or loose engine mounts

Fuel

Check fuel quality

DTC P1599

Check DTC P1599 -- refer to chart.

Exhaust Gas Recirculation (EGR) Valve

Check for EGR valve stuck open.

Electronic Ignition (EI)

Check terminals and wires at EI module.

Powertrain Control Module (PCM)

Check PCM power and grounds.

Vacuum leak

Check for vacuum leak.

Fuel pressure

Check fuel pressure.

Spark plugs and Wires

Check park plugs and wires for arcing or corrosion.

Cylinder Compression

Check cylinder compression.

Long term fuel trim values

Monitor long term fuel trim values on a scan tool to check if system is running rich or lean.