Rough or Unstable Idle

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

POSSIBLE CAUSE ACTION


EGR malfunction, Check EGR system in TESTING
Flange gasket leaking, PROCEDURES
valve open (valve should
be closed at idle)

PCV valve malfunction Check PCV system in TESTING
PROCEDURES

Faulty canister purge Check Evaporative system in
TESTING PROCEDURES

Restricted exhaust system Check Catalytic Converter system
in TESTING PROCEDURES