I feel as if I'm getting tantalizingly close, but no cigar yet. . . .

Here's what I found puttering around today ('72 142E):

When the engine is fully warmed up and running, and I pull the top hose from the auxiliary air valve, the engine races. If I put my palm over the hose, the engine slows precipitously and will die. Per one of the diagnostic guides I'm using, this indicates that the auxiliary air valve is faulty and needs to be replaced.

Does this sound right? (I think it does, as the auxiliary air valve is supposed to be closed once the engine is warm -- but the drop in engine speed when I block the hose with my palm indicates that the valve is still open, even at operating temperature). Black sooty plugs indicate that the engine is running way rich, for what it's worth.

Also did some testing on the throttle switch (what my diagnostic guide refers to as the "flap contact"). Set the throttle stop screw per the guide, and then inserted a .020 in. feeler gauge between the throttle stop screw and its point of contact on the manifold.

Per the guide, " Connect a voltmeter between terminal 17 on the [throttle switch] and ground. Turn on the ignition. Loosen the retainer screw on the [throttle switch] so you can turn it. Turn the contact counterclockwise to stop. the voltmeter should show 0V."

So, far so good . . . Again, per the guide:

"Turn the [throttle switch] clockwise until the voltmeter indicates. Lock the contact exactly where the voltmeter indicates."

My question is -- indicates WHAT? Any voltage at all? A specified voltage? I don't have to turn the throttle switch very far clockwise (from a full counterclockwise stop position) to get SOME voltage reading. But, if I set the throttle switch screws at this point, the idle is way too high.

Can anyone give me any pointers on exactly how to set the throttle switch?

And finally, when trying to set the idle using the idle screw underneath the manifold,I can't get the idle to drop below 900 rpm, even with the screw turned in as far as it will go. As timing on my car (an automatic) is supposed to be set at 800 rpm, I'm a little stuck. Again, this may have to do with the bad auxiliary air valve.

Thanks for any help!