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 Routing"
in Emissions - Check intake manifold
and vacuum components
PCV malfunction Check PCV system in "Testing
Procedures" in Emissions
EGR malfunction Check EGR system in "Testing
Procedures" in Emissions
Initial timing incorrect Check Ignition Timing in "Adjustment
Procedures" in Emissions
Verify vehicle remains in Check oxygen sensor system in "Testing
Closed Loop at steady throttle Procedures" in Emissions
(2500 rpm) and oxygen sensor
is working