Rough, Unstable, or Incorrect Idle, Stalling

ROUGH, UNSTABLE OR INCORRECT IDLE/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.
^ Generator charging output voltage. Repair if less than 13 volts or more than 16 volts with all accessories off.
^ Injector Balance.
^ EVAP canister purge system
^ Minimum air rate
^ Catalytic converter blockage
^ Fuel quality.
^ Powertrain mounts.
^ For DTC P1599 - see chart.
^ EGR pintle valve held open
^ Check Terminals and wires at EI module
^ Check Terminals and wires to crank position sensor
^ PCM power and grounds
^ Fuel pressure
^ Spark plugs and wires
^ Cylinder compression.

Monitor long term fuel trim values on Scan tool if system is running lean (block learn near 147).