High HC -- at High RPM

Condition: 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 intake manifold
and vacuum components.
Check vacuum lines and routing.
See Diagrams




PCV malfunction See Positive Crankcase Ventilation



EGR malfunction See Exhaust Gas Recirculation


Initial timing incorrect Check Ignition Timing.
See Adjustments.



Electronic Spark Advance Refer to Computers and
fault Control Systems.



Verify vehicle remains in Refer to Computers and
Closed Loop at steady throttle Control Systems
(2500 rpm) and oxygen sensor
is working