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 in
or malfunctioning vapor purge system "Testing Procedures" in Emissions



Malfunctioning Closed Loop fuel metering Refer to "Fuel Injection and
system - Exhaust leak or other false Computerized Engine Controls"
indicators "Fooling" oxygen sensor to for testing of the computer
sense a lean condition feedback system



Stuck or restricted PCV Check PCV system in "Testing
valve and/or hose Procedures" in Emissions