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 Refer to Computers And Control Systems

PCV valve malfunction Check PCV 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 Automatic Idle Speed (AIS) motor,

Dirty air filters Clean or replace

Poor or contaminated fuel Recommend higher grade fuel