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 Inspect vacuum hoses for
proper routing and damaged lines
Check intake manifold gasket area



PCV malfunction Check PCV system



EGR malfunction Check EGR system



Initial timing incorrect Check Ignition Timing, see ADJUSTMENT PROCEDURES


Incorrect Spark Advance Check timing advance controls



Verify vehicle is operating in Refer to OXYGEN SENSOR
Closed Loop at steady throttle TESTING
(2500rpm) and oxygen sensor
is working