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. Either condition may be severe enough to cause stalling. Engine idles at incorrect speed.

POSSIBLE CAUSE ACTION

Throttle linkage sticking/binding ^ Check and adjust.



Fuel Metering ^ Check air/fuel ratio, (verify O2 Sensor Voltage).
^ Perform injector balance test.
^ Check fuel pressure.



Incorrect idle speed ^ Perform injector service (cleaning).
^ Check Idle Air Control (IAC) Valve.
^ Check Throttle Valve Minimum Position.



Vacuum Leak ^ Inspect vacuum hoses for proper routing and damaged lines.
^ Check intake manifold, throttle body base and gasket.