Auxiliary Air Valve
The auxiliary air valve, or regulator, provides additional air to the engine to increase idle speed when the engine is cold. It allows air to by-pass the throttle valves which are closed at idle.
A heating coil in the valve is connected to the control pressure regulator and fuel pump circuit. As the coil warms up, it gradually closes the air passage. The valve is calibrated to keep idle smooth without a large speed change as the engine is warming up.