Unusual Idle speeds

Okay, for the past month every time I start up 1886 the engine idles at 2300rpm on cold starts. After a few minutes the idle becomes sporadic, bouncing between 1600rpm and 2200rpm. To describe this, when the idle hits 2200rpm it drops down to 1600rpm fast, it does this like I'm continuously revving the motor. I'm not sure what is causing this problem and it IS getting annoying /ubbthreads/images/graemlins/banghead.gif because when I leave work people think I am revving my car at them at stop lights. However when the engine is at operating temps, this problem goes away. Any help guys? I can post up a video of this problem so you can see/hear what I'm talking about.

 

Check your Idle Speed Control Valve located right under your throttle body. Pull that badboy off and use a voltmeter to check the resistance between the pins. You can see how to do this here. If your ISC is working correctly I would look into blocking off your Fast Idle Air Valve (FIAV). You can find more info on the FIAV here and here. Happy reading and good luck!
-Brian