Rough 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


AT ALL TIMES
EGR malfunction, Check the EGR system
Flange gasket leaking, under TESTING PROCEDURES.
valve open (valve should
be closed at idle).



PCV valve malfunction Check the PCV system under
TESTING PROCEDURES.



AT OPERATING TEMPERATURE
Faulty canister purge Check the Evaporative Emission System
and bowl vent valve under TESTING PROCEDURES.



Restricted exhaust system Check the Catalytic Converter
under TESTING PROCEDURES.



Idle speed too low Check idle speed. Refer to
ADJUSTMENT PROCEDURES.