High HC at High RPM

This condition indicates abnormally high Hydrocarbons with a low or normal Carbon Monoxide content during cruise (2500 rpm).

POSSIBLE CAUSE ACTION

Electrical misfires Check ignition system.



Vacuum leak Check vacuum lines and routing. Refer to
VACUUM AND VAPOR HOSE DIAGRAMS.
Check intake manifold area and vacuum components.



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



EGR malfunction Check the EGR system under
TESTING PROCEDURES.



Initial timing incorrect Check Ignition Timing. Refer to ADJUSTMENT
PROCEDURES.



Incorrect Spark Advance Check Spark Controls. Refer to
COMPUTERIZED ENGINE CONTROLS.



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