I would check for Vacuum leaks , dont start out using cans and cans of carb cleaner looking for your leak. Start out by Unhooking your PCV valve then plug the hose running to it completely. if you start your car and it idles fine then you have a vac leak( it works because Your PCV is basically a controlled Vac leak so blocking the hose makes up for a vac leak somewhere else.) If it is a vac leak look on your throttle body for a screw ( personally I have no idea where it is ) its the last thing listed on the link in this thead that says Idle problem look here first that solid posted . They say to screw it in completly, but this is again another controlled vac leak . I believe ( might wanna check the Shop book ) that it should be set 2.5 turns out. also this sounds stupid but have you messed with the Throttle cable at all? i had the bright idea to take all the slack out of mine, but that messes with the TPS just enough to give you problems sometimes. sorry for the long post but i had the same thing happen with mine , finally took it to a dealer and they found the problem