Rough, Unstable, or Incorrect Idle and Stalling
ROUGH, UNSTABLE OR INCORRECT IDLE, STALLINGDefinition: 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)
^ APP AT IDLE should read YES on Scan tool with engine running and accelerator pedal all the way up.
^ Generator charging output voltage. Repair if less than 13 volts or more than 16 volts with engine running and all accessories Off.
^ Injectors clogged. Perform Injector Balance test.
^ EVAP purge solenoid stuck open
^ EGR valve leaking
^ Catalytic converter blockage (pre or post)
^ Fuel quality
^ Broken or loose engine mounts
^ Check terminals and wires at EI module harness connector
^ ECM power and grounds (securely bolted to the intake manifold)
^ Vacuum leak (Intake leak between MAF sensor and throttle body)
^ Fuel pressure
^ Spark plugs and boots for corrosion/arcing
^ Cylinder compression
Monitor long term fuel trim values on Scan tool if system is running rich or lean.