High HC -- at High RPM

This condition is indicated by 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 vacuum lines and routing.
Check intake manifold
and vacuum components



PCV malfunction Check PCV system. Positive Crankcase Ventilation



EGR malfunction Check EGR system. Exhaust Gas Recirculation



Initial timing incorrect. Check Ignition Timing. Computers and Control Systems



Incorrect Spark Advance Check Spark Controls. Refer to COMPUTERS AND CONTROL SYSTEMS.



Verify vehicle remains in Refer to COMPUTERS AND CONTROL SYSTEMS.
Closed Loop at steady throttle
(2500 rpm) and oxygen sensor
is working