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 SCHEMATIC DIAGRAMS
under EMISSION CONTROLS.



PCV malfunction Check PCv system.



Initial timing incorrect Check Ignition Timing.
See ADJUSTMENT PROCEDURES.



Electronic Spark Advance Refer to COMPUTERIZED ENGINE
fault CONTROLS.



Verify vehicle remains in Refer to COMPUTERIZED
Closed Loop at steady throttle ENGINE CONTROLS
(2500 rpm) and oxygen sensor
is working