Twice in the past month my 92 Civic has exhibited really bad idle behavior in temperatures around 10-20 degrees F. When first starting the engine, it idles at something like 2000-2500 RPMs (by ear; no tach so I can't tell for sure), and after driving for 5-10 minutes, the behavior changes and it cycles between a low idle (maybe 500-800) and the high idle (2000+) in a pattern of about 2 seconds per cycle. The problem goes away entirely once the temperature increases enough.
My assumption is that there's moisture freezing somewhere, likely inside the IAC valve or elsewhere around the throttle body. Tracking down the exact location seems unpleasant (especially considering the weather I'd be working in) so I'd mainly like to know:
Is this cause for any concern aside from obvious things (emissions, mild surging while driving, etc.)?
Is this a common problem with an easy known fix I could try without spending effort trying to track it down myself?