Auxiliary Air Valve
Most models with Bosch AFC fuel injection use an Auxiliary Air Valve (AAV) to shorten engine warm-up time. The AAV supplies additional air into the intake system which increases engine RPM during a cold start.
The AAV consists of an electrically heated bi-metallic strip, movable disc, and air by-pass channel. The heater coil on the bi-metallic strip is energized by the fuel pump relay. Control of the valve is based upon engine temperature; the air by-pass channel is open when engine is cold and gradually closes as temperature rises. At predetermined temperatures, air by-pass channel is blocked and additional airflow stops. See Fig 1 .