Emission Control Systems: Description and Operation

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

EVAPORATIVE EMISSION CONTROL SYSTEM (EVAP)
The EVAP system stores fuel vapor in a charcoal canister when the engine is not running. Stored vapor is drawn into the dynamic chamber and burned when the engine is started.

POSITIVE CRANKCASE VENTILATION SYSTEM (PCV)
The PCV valve is operated by intake manifold vacuum. When running at idle, the valve is opened slightly and a small amount of blow-by gas is drawn in. At higher engine speeds, the valve opens further and more blow-by gas is drawn in. The system relieves crankcase pressure without allowing vapors to escape to atmosphere.

THREE WAY CATALYTIC CONVERTER (TWC)
Catalytic converters stimulate chemical reactions that change CO, HC, and NOx into carbon dioxide, water vapor, and nitrogen gas. Catalyst elements used are the metals platinum, palladium, and rhodium.