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, refer to "Diagnostic Aids" found in Diagnostic Trouble Code 26 under Computers and Control Systems/Procedures/Diagnostic Charts.

^ If EMISSION TEST shows excessive NOx, check items which cause vehicle to run lean or too hot.

Cooling System
If engine is running too hot or too cold:
^ CHECK: Engine coolant level.
- CHECK: Engine thermostat for faulty part (always open) or for wrong heat range.
- CHECK: Coolant fan operation.

Fuel System
^ NOTICE: If the system is running:

Lean - Refer to "Diagnostic Aids" found in Diagnostic Trouble Code 25 under Computers and Control Systems/Procedures/Diagnostic Charts.

Rich - Refer to "Diagnostic Aids" found in Diagnostic Trouble Code 26 under Computers and Control Systems/Procedures/Diagnostic Charts.


^ CHECK: Fuel pressure.
^ CHECK: Fuel injector spray balance.
^ CHECK: For properly installed fuel cap.
^ CHECK: EVAP canister for fuel loading.

Ignition System
^ CHECK: Ignition timing. Refer to "Vehicle Emission Control Information" label.
^ CHECK: Spark plugs, plug wires, and ignition components.

Additional Checks
^ CHECK: For vacuum leaks.
^ CHECK: For lead contamination for three-way catalytic converter (TWC) or warm up three-way catalytic converter (WU-TWC) (look for the removal of fuel filler neck restrictor).
^ CHECK: Carbon buildup. Remove carbon with top engine cleaner. Follow instructions on can.
^ CHECK: For correct ECM/PCM calibration (see Service Bulletins).
^ CHECK: PCV valve for being plugged, stuck or blocked PCV hose or fuel in the crankcase.