System Description

Fig. 1 Air injection system (Typical):

This system, Fig. 1, is used to reduce carbon monoxide (CO) and hydrocarbon (HC) emissions by adding a controlled amount of air to the exhaust gases in the exhaust system. This addition of air causes further oxidation of the exhaust gases with an appreciable reduction of carbon monoxide and hydrocarbon emissions.
This system consists of an air pump, an [1][2]air switching valve, a check valve, an air manifold and the necessary tubes and hoses to connect the various components. Cylinder heads used on engines with this system have drilled passages to conduct the air to the exhaust ports.
The air injection system is designed so that air injection will not interfere with the ability of the EGR system to control NOx emissions and on vehicles equipped with an oxygen sensor, to ensure air-fuel distribution for maximum fuel economy. Air is injected at the exhaust ports for a short period during engine warm-up, which assists in the oxidation process in the upstream catalyst. On 6 and V8 engines, the air flow is then switched to a point downstream where it will assist the oxidation process in the main catalyst. On 6 cylinder engines, the downstream location is in the exhaust pipe, behind the upstream catalyst. On V8 engines the downstream location is in the main catalyst between the reduction and oxidation catalyst. On 4-97.4/1.6L L4-135/2.2L and 4-135/2.2L engines, after engine warm-up, the air flow is switched to a point in the 3-way catalyst between the reduction and oxidation catalysts reducing CO and HC emissions. On all 1982 and 1983-84 4-97.4/1.6L L4-135/2.2L and 4-135/2.2L engines, air flow switching is controlled by the CCEVS or by a vacuum solenoid. On 1983-86 6 and V8 engines and 1985-88 4 cylinder engines, air flow switching is controlled by the CVSCO or by a vacuum solenoid.