Auxiliary Air Regulator
On the Type 4 engine, the auxiliary air regulator is located immediately behind the intake air distributor. It's a cylindrical object with an electrical connection on one end and two large air hoses. One hose comes from the S-boot after the air flow meter and goes into one end of the auxiliary air regulator and the other hose goes from the regulator to the intake air distributor.
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The auxiliary air regulator provides for a slightly fast idle for a cold engine. It does this by allowing more air in, bypassing the closed throttle valve. It does not, however, change the fuel/air mixture because the air entering the auxiliary air regulator has already been measured by the air flow meter. It just lets some air bypass the throttle body for a fast idle to help keep the cold engine running.
There is a rotary valve in the housing, with one hole in it. This valve is connected to a bimetallic strip. When the engine is cold, the bimetallic strip rotates the valve so that the hole is aligned with the two air hoses -- air can pass through the valve. When the ignition is turned on, a heating element begins to warm the bimetallic strip. As the strip warms, it begins to close the valve. From the coldest, the valve will close in about 8 minutes. When fully warm, no air will pass through the regulator.
The regulator can be tested by blowing through it with the engine cold -- air should pass freely. When the engine is warm, you should not be able to blow through it.
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