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.
Check intake manifold and vacuum components.



Saturated fuel evaporative canister
or malfunctioning vapor purge system 1. SEE EVAPORATIVE EMISSION CONTROL (EVAP) SYSTEM.
If OK, go to step 2.
2. Check Evaporative System electronic controls.



PCV malfunction Check PCV system.



EGR malfunction 1. Check EGR system.
If OK, proceed to step 2
2. Check EGR electronic controls.



Restricted exhaust Check Catalytic Converter.



Initial timing incorrect Check Ignition Timing.



Incorrect Spark Advance Check Spark Controls (SC).



Verify vehicle remains in Closed
Loop at steady throttle (2500 rpm)
and oxygen sensor is working.



Fuel Metering 1. Check Air/Fuel ratio, fuel pressure, and regulator operation.
2. Perform injector balance test.
3. Service Fuel Injectors (Pressure cleaner).