Emission Control Systems: Description and Operation

Many methods have been used to meet increasingly tough emission control standards. These started with positive crankcase ventilation (PCV) valves and progressed to air pumps, fuel vapor canisters, EGR systems, catalytic converters and other systems. Changes have also been made to engine compression, ignition timing and carburetors. These standards are being met using electronic controls and several other components which are listed in EMISSION SYSTEMS APPLICATION. Also refer to the COMPUTERIZED ENGINE CONTROLS section where necessary.