My 93 945t has developed a weird idle problem, which I think is directly related to the record low temps we've been having in NYC, because this only happens when it's mind-numbingly cold. I haven't been able to find a specific remedy in the FAQ, so perhaps there's someone else out there with similar problems? -

She starts great every time, even with the original 11-year old battery. But then the idle speed will go up-down-up-down in a very regular pattern - almost like a metronome or clock ticking. This up-down pattern starts almost imperceptibly, but as it continues the gap between low and high widens to about 1500-2000 rpm at the top, and almost 0 at the bottom - at which point the car almost stalls, and I'll throw it into neutral and rev it a little bit to keep it going. This only happens at idle, the car works perfectly when moving. And it goes away when she warms up. Subsequent warm starts have no problems, and in warmer weather (above freezing) no problems at all.

My first guess would be something in the IAC or throttle body sticking, not that there's much I can do with that in this weather! But could a bad (or possibly dying) AMM do this? Or could this be a sign that something else is failing that I should replace when it thaws out?

Thanks!