Emission Control Systems: Description and Operation

Fig. 133 System Outline:

To reduce emissions, these vehicles use a deceleration control system, high altitude compensation system, evaporative emission control system, positive crankcase ventilation system, three-way converter, and electronic gasoline injection.

EVAPORATIVE EMISSION CONTROL SYSTEM (EVAP)
The evaporative emission control system stores fuel vapor in a charcoal canister. Fuel vapor is stored until drawn into the dynamic chamber and burned when the engine is running.

POSITIVE CRANKCASE VENTILATION SYSTEM (PCV)
The PCV valve is operated by intake manifold vacuum. When the engine is running at idle, the valve is opened slightly and a small amount of blow-by gas is drawn into the engine. At higher engine speeds, the valve opens further and a larger amount of blow-by gas is drawn into the engine.

THREE WAY CATALYTIC CONVERTER (TWC)
The catalytic converter stimulates reactions that change CO, HC, and NOx into carbon dioxide, water vapor, and nitrogen gas. Platinum, palladium, and rhodium act as catalysts to stimulate the necessary chemical reactions.