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.


SYMPTOMS OCCUR AT ALL TIMES

POSSIBLE CAUSE
EGR malfunction.
Flange gasket leaking.
Valve open (valve should be closed at idle)

ACTION
Check EGR system.



POSSIBLE CAUSE
Air management valves malfunctioning.
No air to ports while in closed loop.

ACTION
Check Air Injection.



POSSIBLE CAUSE
PCV valve malfunction.

ACTION
Check PCV system.



SYMPTOMS OCCUR AT OPERATING TEMPERATURE

POSSIBLE CAUSE
Faulty canister purge.

ACTION
Check Evaporative System.



POSSIBLE CAUSE
Restricted exhaust system.

ACTION
Check Catalytic Converter.



POSSIBLE CAUSE
Idle speed too low.

ACTION
Check idle load compensator devices. See "Computers and Control Systems".