505 L4-1971cc XN (1983)
Auxiliary Air Valve (Idle Speed): Description and Operation
The auxiliary air device is an electrically operated valve which allows air to bypass the closed throttle plate during cold engine operation. The additional
air compensates for mixture enrichment provided by the cold start valve and control pressure regulator and provides a ``fast idle'' to prevent stalling
during warm up. The valve opening is controlled by a bi-metallic element which responds to temperature, and the element is heated both by engine heat
and an internal heating coil.
When the valve is cold the bypass channel is open and air is allowed to bypass the throttle plate. When the engine is started voltage is applied to the
valve heating coil through the fuel pump relay. The bi-metal element is heated by both the engine and the internal coil causing it to expand, and the
bypass channel is gradually closed.
