Excessive Exhaust Emissions (Odors)

Definition: Vehicle fails an emission test. May also have excessive "rotten egg" smell (hydrogen sulfide).

^ Perform "Diagnostic Circuit Check - Calif".

^ Perform "System Performance Check - Calif".

^ If test shows excessive CO and HC, (also has excessive odors):

- Check items which cause vehicle to run rich.

^ Make sure engine is at normal operating temperature.

^ Visually check hoses for splits, kinks and proper connections, as shown on Vehicle Emission Control Information label.

^ Remove air cleaner and check air filter for dirt or being plugged. Replace as necessary.

^ Check for mis-adjusted idle mixture if plugs are removed.

^ Check choke valve and linkage for sticking of faulty operation.

^ Check choke, vacuum breaks and fast idle adjustments.

^ Check for stuck PCV valve or obstructed hose.

^ Check for lead contamination of catalytic converter, Check for absence of filler neck restrictor.

^ Check operation of air management system. See Chart C-6.

^ Check carburetor for flooding.

^ Check float level using external float gage.

^ Check canister for loading and check purge system for proper operation. Chart C-3.

^ Check for incorrect idle speed.

^ Check for incorrect timing. See Vehicle Emission Control Information label.

^ Check condition of spark plugs, plug wires and distributor cap.


^ If test shows excessive NOx:


- Check items which cause vehicle to run lean, or to run too hot.


^ Check EGR valve for not opening. See Chart C-7.


^ Check for vacuum leaks.

^ Check for inoperative THERMAC.


^ Check coolant system and coolant fan for proper operation.


^ Remove carbon with top engine cleaner. Follow instructions on can.


^ Check ignition timing for excessive base advance. See Vehicle Emission Control Information label.