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), refer to COMPUTERS AND CONTROL SYSTEMS.
Restricted or leaking injector(s) ^ Fuel Injector Balance Test Procedure
^ Check fuel pump and pressure regulator.

Incorrect idle speed ^ Check Idle Air Control (IAC) Valve. Refer to COMPUTERS AND CONTROL SYSTEMS/DIAGNOSIS, TESTING AND INSPECTION PROCEDURES.
^ Check throttle valve closed throttle stop adjustment

Vacuum Leak ^ Inspect vacuum hoses for improper routing and/or damaged lines
^ Check intake manifold, throttle body base and gasket