Rough, Unstable, or Incorrect Idle and Stalling

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.

Check:
^ Misfire counts using Scan tool (if any exist)
^ Throttle linkage for sticking or binding
^ Throttle position sensor should read zero percent at idle on Scan tool.
^ IAC System. Refer to air intakes system.
^ Generator charging output voltage. Repair if less than 11 volts or more than 16 volts with all accessories off.
^ Injector Balance test. Refer to fuel system.
^ [1][2]EVAP emissions system
^ Minimum air rate
^ Catalytic converter blockage
^ Fuel quality. Refer to fuel system.
^ Powertrain mounts. Refer to "Chassis."
^ For DTC P1599 - refer to chart. P1599
^ Cheek Terminals and wires at EI module.
^ Cheek Terminals and wires to crankshaft position sensor.
^ PCM power and grounds
^ Fuel pressure
^ Spark plugs and boots
^ Cylinder compression. Refer to Engine.

Monitor long term fuel trim values on Scan tool if system is running lean (long term fuel trim is significantly positive). (Refer to P0171.) P0171