High HC - at High RPM

This condition, abnormally high Hydrocarbons with low or normal CO during cruise (2500 rpm), may indicate a problem in one or more of the areas listed below.

POSSIBLE CAUSE ACTION


Electrical misfires Check ignition system



Restricted fuel system or clogged injectors Refer to "FUEL DELIVERY AND AIR INDUCTION, perform fuel system tests.



Lean Air-Fuel ratio Check oxygen sensor and feedback
Contaminated or defective oxygen sensor system



Vacuum leak Check vacuum lines and routing.
See SCHEMATIC AND ROUTING DIAGRAMS.
Check intake manifold, and vacuum components.



PCV malfunction Check PCV system.



Incorrect Spark Advance Check Spark Controls (EST, ESC etc..).



EGR malfunction Check EGR system.