Corey, I had this bad!!
I did all the vac leaks, intake leaks, plugs, wires, fuel filter etc etc.
then I started doing some research.
Turns out that if its not the above, its either the Idle Speed Control motor, or the Fast Idle Air Valve.
The ISC is easy to replace, but don't buy it from Satan. It's like $400 or more, plus tax. Get one from a 92 Elantra 1.8 from Hyundai. Its a Mitsu part and a perfect fit. No probs and I've had mine in for almost a year.
If its not the ISC, you have to do a bit of surgery. The FAIV is part of the throttle body. You have to take it off, and take the bottom part out and modify it a bit. Low cost, but a bit of a time consuming thing.
3 tips on this. When you reroute the coolant from the thermostat housing back to the heater hose, get a new hose. the extra stress on my old one caused it to blow in 2 days, and they are only $10 or so.
Second tip, take out the battery.
3rd tip, have some coolant on hand.
here is a link to a guys site that has good instructions on it.
http://www.vallotton.com/fiavblockoff.aspalso, I did not make a metal blockoff plate, I just used tough impregnated cork gasket material. It is an eighth thick, and pretty tough. I was gonna just use that to see if the problem was solved(it was and very well), and then make a metal one later, but I've had no need.
Best of luck
