B150 1/2 Ton Van L6-225 3.7L VIN E 1-bbl (1982)
Air Injection Control Valve: Description and Operation
Air Switching Valve
Fig. 4
This valve, Fig. 4, switches air injection from the exhaust ports to an injection point further downstream in the exhaust system after engine
warm-up so that air injection will not offset the effect on NOx emissions by the EGR.
When the engine is warming up and NOx emissions are low, air injection to the exhaust ports is acceptable, however as the gases become hotter
they tend to oxidize more rapidly by the addition of secondary air causing an increase of NOx emissions. At this time, the air switching valve
switches the air injection.
A vacuum signal from the CCEVS causes the switching valve to open allowing all air injection into the exhaust ports. When CCEVS shuts off
vacuum to the switching valve, the valve closes and bypasses most of the air injection to the injection point downstream in the exhaust system. A
bleed hole in the switching valve permits a small amount of air pump air to be injected into the exhaust ports at all times to assist in CO and HC
reduction.
