I have a 2001 Wrangler well maintained and has been running very well.  Just recently when i start it up (no foot on the gas) the idle starts surging up and down. Sometimes it surges up and stays up reving somewhere between 2000-3000.  If I push on the gas and rev it with my foot it will come back down or stop surging and idle correctly.  I'm not sure what could be causing it.  Any help would be greatly appreciated.  

do you have a cold air intake? my old 00 tj did this every morning on cold start up. i think it had something to do with the cold air intake.  

When the idle on my '99 TJ started to do funky things it turned out to be the idle control motor, it's the one on the throttle body that is round. It may ether be bad or just need a cleaning, sometimes they just get dirty and get stuck.