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"
in Emissions - Check intake manifold
and vacuum components


PCV malfunction Check PCV system in "Testing
Procedures" in Emissions


EGR malfunction (Except Montero) Check EGR system in "Testing
Procedures" in Emissions


Initial timing incorrect Check Ignition Timing in "Adjustment
Procedures" in Emissions


Incorrect Spark Advance Check Spark Controls in
"Fuel Injection and Computerized Engine Controls"


Verify vehicle remains in Refer to "Fuel Injection and
Closed Loop at steady throttle Computerized Engine Controls"
(2500 rpm) and oxygen sensor for Self-Diagnostic procedures
is working