High HC at High RPM

DEFINITION
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
- Intake manifold and vacuum components



[1][2]PCV malfunction Check PCV system.




Initial timing incorrect Check Ignition timing




Incorrect spark advance Check Spark controls (EST, ESC etc.)



EGR malfunction Check EGR system.



Vehicle remains in Perform O2 sensor test
open Loop at steady throttle refer to OXYGEN SENSOR TESTING/
(2500 rpm) DIAGNOSIS, TESTING AND INSPECTION PROCEDURES
in COMPUTERS AND CONTROL SYSTEMS