Air By-Pass Valve

During normal operation, air pump system air passes through by-pass valve to exhaust ports. On deceleration, large amount of unburned air/fuel mixture reaches exhaust port area. Adding fresh air would cause afterburn.

When by-pass valve manifold connection senses high vacuum level, by-pass valve momentarily diverts part of air pump air back to inlet side of air pump while part is directed into intake manifold to help balance air/fuel mixture during deceleration.