Air Injection: Description and Operation

SYSTEM OPERATION

The purpose of the AIR System is to reduce the amount of emissions in the exhaust, heat the catalytic converter quickly on engine start-up, and to start conversion of pollutants quickly.

This system has two specific functions. First, during cold engine start-up (open loop), air flows through a reed valve assembly to a point just ahead of the oxygen sensor. Second, after the engine is at normal operating temperature and after the 10 second timer has elapsed, air is diverted, by the vacuum switching valve, to the atmosphere. The system is composed of a reed valve assembly, a vacuum actuator, and a vacuum switching valve.

REED VALVE ASSEMBLY

The reed valve assembly is part of the pulse air system, and it is attached to the air cleaner assembly. This assembly operates on exhaust pulses to provide air injection to the exhaust manifold just upstream of the oxygen sensor. The reed valves act as one-way valves that are open during slight acceleration and cruising speeds, but closed during deceleration to prevent exhaust gases from entering the air cleaner assembly.

VACUUM SWITCHING VALVE

The vacuum switching valve has two specific functions. It allows vacuum to flow to either the reed valve assembly or vent to the atmosphere.

This valve is controlled by the ECM and a timer. During cold operation a vacuum signal is allowed to flow through the vacuum switching valve and out to the reed valve assembly, thus allowing air output to flow to a point just upstream of the oxygen sensor. Once the engine warms up to normal operating temperature, the vacuum switching valve allows the vacuum signal to bleed off to the atmosphere, thus shutting "OFF" the vacuum signal to the reed valve assembly. When there is no manifold vacuum signal to the reed valve assembly, the air injection output is directed to the atmosphere.