High HC, Low or Normal CO - 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



ECCS system malfunction. Refer to On Board Diagnostics.



Electrical misfires. Check ignition system.



Vacuum leak. Check vacuum lines and routing in
"Vacuum and Vapor Hose Routing"
in Emissions also check intake manifold
and vacuum components.



PCV malfunction. Check PCV system.




EGR malfunction. Check EGR system.




Initial timing incorrect. Check ignition timing.



Verify vehicle remains in
closed loop at steady throttle
(2000 rpm) and Heated Oxygen Sensors
are working.