I have an 87 with the M47 manual trans. My car is stored in an unheated garage, so when I start it cold, it idles at about 1K for a few seconds and then idles down to about 800 rpm. Idle is rock steady and has always been the same. It was very cold here over the weekend. It was 10 degrees when I started the car and the same routine occurred: 1K for a few seconds, down to 800. I took a little ride and it warmed up. After warm-up, the idle increased slightly to about 9 or 950 rpm. Before the cold weather, I cleaned the throttle body and MAF, replace the IAC valve with a new one and lubricated the throttle cable and linkage. Today I checked for vacuum leaks but didn't find any. It was in the 30's today and the car is still idling slightly high after it warms up. Any ideas?
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Hmm. Short of the new IAC being faulty or sticking, I'd say maybe the throttle stop is off or the switch isn't working perfectly.

Why did you replace the IAC valve?

Good Luck
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1990 740 Turbo, on its way to stock specs, maybe beyond

I replaced the IAC valve as a maintenance issue. The old one was working fine, but had about 350K miles on it, so I figured I would change it before it went bad.
The new one had been sitting on a shelf for several years. Would shooting a little WD 40 into the new one be a good thing?
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Well, I'd try putting in the one that was there. Lubricating them with some WD-40 or penetrating oil is a good idea. Put a bunch into the door mechanism(This is the sealed type, right? No big metal clamp in the middle?), then spin the motor so that the door flops back and forth. Repeat until it moves easily and always closes.
If it's got a big clamp in the middle, DON'T put WD-40 into it. It can be disassembled and cleaned and lubricated, but getting the metal clamp apart can be a PITA.

Good Luck, hopefully it's the IAC valve.