Excessive Exhaust Emissions (Odors)

DEFINITION
Vehicle fails an emission test. Vehicle has excessive "rotten egg" smell. Excessive odors do not necessarily indicate excessive emissions.

PRELIMINARY CHECKS
^ If EMISSION TEST shows excessive CO and HC, check items which cause vehicle to run RICH (HO2S voltage above 450 mV). Make sure engine is at normal operating temperature.
^ If EMISSION TEST shows excessive NOx, check items which cause vehicle to run LEAN or too hot.

SENSORS

NOTE: If a Tech 1 scan tool (or equivalent) indicates a very high engine coolant temperature and the system is running LEAN, check the Cooling System and for proper operation.

FUEL SYSTEM
^ Check for proper fuel filler cap.
^ Check fuel pressure.
Refer to Chart A-7B Fuel System Pressure Check. Testing and Inspection

Also refer to On-Board Diagnostic System Check.

NOTE: If test shows excessive NOx, check items which cause vehicle to run LEAN or too hot.

^ Check EVAP canister for proper operation, refer to Chart C-3A Evaporative Emission Canister Purge Valve Check. Testing and Inspection
^ Check fuel injectors. Perform fuel system pressure test and injector balance test.

IGNITION SYSTEM
^ Check for incorrect timing or excessive advance. See underhood "Vehicle Emission Control Information" label.
^ Check ignition system. Refer to Ignition System / System Diagnosis.
^ Check spark plugs, plug wires, and ignition components.

ADDITIONAL CHECKS
^ Check for vacuum leaks.
^ Check for lead contamination of three way catalytic converter (look for the removal of fuel filler neck restrictor).
^ Check for carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
^ Check EGR valve for not opening, refer to Chart C-7A EGR System Check. Testing and Inspection
^ Check PCV valve for being plugged, stuck, or blocked PCV valve hose, or fuel in the crankcase.