High CO, Low or Normal HC - at Idle

Symptom: High Carbon Monoxide, normal or low Hydrocarbons at idle.

POSSIBLE CAUSE ACTION


Rich Air-Fuel mixture ^ Check fuel pressure.

^ Check O2 sensor.

^ Perform injector balance test (SFI only).


Dirty air filter ^ Clean or replace


Saturated fuel EVAP canister ^ Check Evaporative system.
or malfunctioning vapor purge system.


Stuck or restricted PCV valve and/or hose ^ Check PCV system.
Positive Crankcase Ventilation


Malfunctioning Closed Loop fuel metering ^ For testing of the computer
system - Exhaust leak or other false feedback system,
indicators "Fooling" oxygen sensor. SEE COMPUTERS AND CONTROL SYSTEMS.
(Sensing a lean condition.)