Auxiliary Air Valve question Options

[torakki]

This is on a '74 2.0. This car's been on and off the back burner for a number of years. (To many cars). It now runs very well, "Except", when it's cold, it idles perfect. As it warms, (about 2 minutes) the idle gets faster to about 1800 rpm. After a 15-to-20-minute drive, I shut it off. Restart a few minutes later and the idle is slow to wont idle fast enough to keep running. So, I'm checking the Auxiliary air valve (I took it apart) and when it's cold, it's open halfway. When it gets warm, it closes. Shouldn't it be opening when warm to let in more air to keep the idle speed up? In other words, lean out the mixture? I would think, when cold, it should be closed to richen up the fuel and warm, open to lean out.
Am I 180 degrees off?
Thanks for any input.

[torakki]

I am kinda leaning towards, no leaks, since I installed a new vacuum line kit on the engine and have gone through it multiple times. Also, when I pull the vacuum hose off the AAV, (creating a leak), engine idles at 2K.
I've replaced the CHT sensor twice, new MPS, replaced the, I believe it's called, ambient air temp sensor and all the normal things like ign. wires, plugs, cap, rotor, points and everything I could think of.
I wonder if poor valve adjustment could cause slow idle? Sometimes I imagine some clatter but then I think, no, that's a normal sound.
Thanks for all the replies. Now I know how the AAV works.