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 Inspect vacuum hoses for
proper routing and damaged lines
Check intake manifold gasket area
PCV malfunction Check PCV system
EGR malfunction Check EGR system
Incorrect spark advance Refer to computerized spark control
Verify vehicle is operating in Refer to ON-BOARD DIAGNOSTICS
Closed Loop at steady throttle
(2500rpm) and oxygen sensor is
working