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



CEC input sensor(s) malfunction ^ SEE Computers and Control Systems


CCV valve malfunction ^ Check CCV system, Positive Crankcase Ventilation


Incorrect Air-Fuel mixture ^ Check Air-Fuel ratio, perform injector balance test, inspect regulator operation (check vacuum line and return hose), check fuel pressure


EGR malfunction ^ Check EGR system, Exhaust Gas Recirculation


Faulty canister purge ^ Check Fuel Evaporative System, Evaporative Emissions System


Restricted exhaust system ^ Check Catalytic Converter, Catalytic Converter


Idle speed too low ^ Check operation of Idle Air Control (IAC) motor,


Dirty air filters ^ Clean or replace


Poor or contaminated fuel ^ Recommend higher grade fuel