High CO & HC - at Idle

Symptom: High Carbon Monoxide (CO), and Hydrocarbons (HC), at idle.

POSSIBLE CAUSE ACTION


Dirty (clogged), air filter ^ Clean or replace filter.


Very rich Air-Fuel mixture ^ Check fuel pressure.

^ Check O2 sensor output voltage.

^ Perform injector balance test (SFI only).


Faulty Fuel Evaporative system, ^ Check Fuel Evaporative system.
vapor lines, purge solenoid
and valves.


Fuel in crankcase being ^ Remove PCV Valve
sucked through PCV Valve from crankcase, (so [1][2]PCV sucks
fresh air), and retest emissions.
Diagnose and repair cause, change oil and retest.