High CO and HC at Idle

This condition, at idle, indicates abnormally high Carbon Monoxide and Hydrocarbons.

POSSIBLE CAUSE ACTION


VERY RICH Air-Fuel mixture

Carbureted Check Air/Fuel ratio, flooding or
leaking carburetor, 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.



Malfunctioning air pump Check Air Injection system.
See AIR INJECTION SYSTEM in TESTING PROCEDURES.



Faulty Fuel Evaporative system, Check Fuel Evaporative system.
vapor lines, purge solenoid See EVAPORATIVE CONTROL SYSTEM in
and valves TESTING PROCEDURES.



Fuel in crankcase being Remove PCV from crankcase
sucked through PCV valve and retest emissions.