High HC - at High RPM

This condition indicates abnormally high Hydrocarbons with low or normal CO during cruise (2500 rpm).

POSSIBLE CAUSE ACTION


Electrical misfires Check ignition system



Vacuum leak Check vacuum lines and routing in
VACUUM AND VAPOR HOSE DIAGRAMS
Check intake manifold
and vacuum components



[1][2]PCV malfunction Check PCV system under TESTING
PROCEDURES.



EGR malfunction 1. Check EGR system under TESTING
PROCEDURES. If OK, step 2
2. Check EGR electronic controls.
Refer to COMPUTERIZED ENGINE CONTROLS.




Initial timing incorrect Check Ignition Timing under
ADJUSTMENT PROCEDURES.



Incorrect Spark Advance Check Spark Controls (SCC).
Refer to COMPUTERIZED ENGINE CONTROLS



Verify vehicle remains in Refer to COMPUTERIZED
Closed Loop at steady throttle ENGINE CONTROLS for
(2500 rpm) and oxygen sensor Self-Diagnostic procedures
is working