High HC - at High RPM

SYMPTOM:
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"
Check intake manifold
and vacuum components


PCV malfunction Check Positive Crankcase Ventilation system in "Testing
Procedures"


EGR malfunction Check Exhaust Gas Recirculation system in "Testing
Procedures"


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 "Computerized Engine Controls"
Closed Loop at steady throttle for Self-Diagnostic procedures
(2500 rpm) and oxygen sensor
is working