I have been dealing with this idle for over a year now and i am getting so irritated by not being able to diagnos it. This is what it does.
The idle tipicaly stays around 900-1000 but every once in a while for no reason. doesn't matter how hot the car is or the outside temp. wheather doesn't affect it, open loop vs. closed loop doesn't matter, the idle will jump to about 1100-2000. now it will stay at this idle for a while, it doesn't jump around. Then a while after driving i will notice it's running fine but then it will do it again sometimes.
So heres what i have done to try and solve the problem so far...
-Replaced any questionable vaccum lines
-Replaced and adjusted TPS and IAC
-Cleaned and lubed the TB
-Added a second throttle return spring

I believe that is all. I also had a code 36 come up just recently but the MAF burnoff relays are only 6 months old so i reset the ECM and it hasn't caome up since. not sure if that helps.

I'm thinking its a vaccum leak but can't find it anywhere. please someone help me.