High CO, Low or Normal HC - at Idle

SYMPTOM:
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 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 Refer to "Computers and
system - Exhaust leak or other false Control Systems"
indicators "Fooling" oxygen sensor to for testing of the computer
sense a lean condition feedback system


Stuck or restricted [1][2]PCV Check PCV system in "Testing
valve and/or hose Procedures" in Emissions