High HC -- at High RPM

Condition: Abnormally high hydrocarbon emissions with low or normal carbon monoxide emissions during cruise (2500 rpm).

POSSIBLE CAUSE ACTION


Electrical misfires Check ignition system



Vacuum leak Check intake manifold
and vacuum components.
Check vacuum lines and routing.




PCV malfunction See Positive Crankcase Ventilation System



EGR malfunction See Exhaust Gas Recirculation System


Initial timing incorrect Check Ignition Timing.
See Adjustments



Electronic Spark Advance
fault See Computers and Control Systems



Verify vehicle remains in
Closed Loop at steady throttle
(2500 rpm) and oxygen sensor
is working See Computers and Control Systems