Rough Unstable Idle

The engine runs unevenly. In severe cases, the car may actually shake. The engine idle may hunt or fluctuate in rpm and may be bad enough to stall.

POSSIBLE CAUSES

PCV Valve Malfunction
- Check PCV system in "Testing Procedures"

Faulty Canister Purge Valve (at operating temperature)
- Check Evaporative system in "Testing Procedures"

Restricted Exhaust System
- Check Catalytic Converter system in "Testing Procedure"

Idle Speed Too Low
- Check idle speed in "Testing Procedures" and in "Adjustment Procedure"