High CO, Low or Normal HC at Idle

This condition, at idle, indicates abnormally high Carbon Monoxide while the Hydrocarbons remain normal or low.

POSSIBLE CAUSE ACTION


Rich Air-Fuel mixture


Carbureted Check Air/Fuel ratio, partially
closed choke, high fuel level (floats),
and dirty air bleeds.



Fuel Injected Check Air/Fuel ratio,
perform injector balance test,
inspect regulator operation,
(check vacuum line and return hose),
check fuel pressure.



Dirty air filters Clean or replace.



Saturated fuel evaporative canister Check evaporative system. See EVAPORATIVE
or malfunctioning vapor purge system CONTROL SYSTEM in TESTING PROCEDURES.




Stuck or restricted [1][2]PCV Check PCV system.
valve and/or hose See CRANKCASE or POSITIVE
CRANKCASE VENTILATION SYSTEM in TESTING PROCEDURES.