High HC and CO at High RPM

This condition indicates abnormally high Carbon Monoxide and Hydrocarbons 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



Faulty bowl vent/canister purge system Check Evaporative System in
TESTING PROCEDURES



PCV malfunction Check PCV system in TESTING
PROCEDURES



EGR malfunction Check EGR system in TESTING
PROCEDURES



Restricted exhaust Check Catalytic Converter in
TESTING PROCEDURES



Initial timing incorrect Check Ignition Timing in ADJUSTMENT
PROCEDURES



Incorrect Spark Advance Check Spark Controls in
COMPUTERIZED ENGINE CONTROLS



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



Fuel metering malfunction Check fuel pressure
Perform injector balance test
Inspect regulator operation
(check vacuum line and return hose),
Service Fuel Injectors (Pressure cleaner)