Emission Control Systems: Description and Operation

Emission Control System:

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

EVAPORATIVE EMISSION CONTROL SYSTEM (EVAP)
The EVAP system stores fuel vapor in a charcoal canister when the engine is not running. Vapor is stored in the canister until it is drawn into the dynamic chamber and burned under specified operating conditions.

POSITIVE CRANKCASE VENTILATION SYSTEM (PCV)
The PCV valve is operated by intake manifold vacuum. When the engine is running at idle, the valve opens 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 in.

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 are catalysts used to stimulate these reactions.