High HC - At High RPM

This condition indicates abnormally high Hydrocarbons (HC) with low or normal Carbon Monoxide (CO) 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.


EGR malfunction 1. Check EGR system.
If OK, proceed to step 2
2. Check EGR electronic controls.



Initial timing incorrect Check Ignition Timing.



Incorrect Spark Advance Check Spark Controls (SC).



Verify vehicle remains in Closed
Loop at steady throttle (2500 rpm)
and oxygen sensor is working.