Rough/Unstable Idle or Stalls

Symptom: The engine runs unevenly at idle. If bad enough, the car may shake. Also, the idle may vary in RPM (called "hunting"). Either condition may be severe enough to cause stalling.

NOTE: This symptom may be caused by an accumulation of intake valve deposits and/or clogged fuel injectors. Refer to the TSB for further information.

POSSIBLE CAUSES
Ignition System
- Ignition timing.

Fuel System
- Injector balance.
- Idle Speed Control.
- Throttle position sensor.
- Air flow sensor.
- Oxygen sensor.

Emission Systems
- EGR "ON" while idling will cause roughness, stalling, and hard starting.
- PCV valve operation.
- Perform the usual checks for obvious problems (vacuum leaks, vacuum and electrical circuits correctly connected arcing at distributor or plug wires etc.)

Starting and Charging Systems
- Battery cables and ground straps should be clean and secure.

Computers and Control Systems
- Power Steering load sensor.