High HC 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


Electrical misfires Check ignition system



Vacuum leak Check vacuum lines and routing in
"Vacuum and Vapor Hose Diagrams"
- Check intake manifold
and vacuum components



PCV malfunction Check PCV system in "Testing
Procedures"



EGR malfunction Check EGR system in "Testing
Procedures" in Emissions



Initial timing incorrect Check Ignition Timing in "Adjustment
Procedures"



Incorrect Spark Advance Check Spark Controls in
"Computers And Control Systems"



Verify vehicle remains in Refer to
Closed Loop at steady throttle "Computers And Control Systems" for
(2500 rpm) and oxygen sensor Self-Diagnostic procedures
is working