High CO, Low or Normal HC at Idle

This condition, at idle, is indicated by abnormally high carbon monoxide emissions while the hydrocarbon emissions remain normal or low.

POSSIBLE CAUSE ACTION


Rich Air-Fuel mixture


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



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



Dirty air filter(s) 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 Check fuel system controls
system - Exhaust leak or other false and integrity of exhaust system
indicators "Fooling" oxygen sensor to
sense a lean condition





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