My 93 Taurus will idle high and low (sometimes dying in the process) when I start the car. Sometimes when I don't have my foot on the gas while driving, the engine will start do this see-saw again. I've tried changing the Throttle Position Sensor (TPS) with no luck in solving the problem.

Sounds like the IAC needs replacing.

Hey if it runs up when on but you are not giving it gas and only then. I would have to say check to make sure your upper intake manifold is seated properly. A leak could do it. I did some work on mine and put it back in place. A bold striped and the manifold did not seat properly. It only ranged between a 500 to 750rpm fall or gain.

My 93 Taurus will idle high and low (sometimes dying in the process) when I start the car. Sometimes when I don't have my foot on the gas while driving, the engine will start do this see-saw again. I've tried changing the Throttle Position Sensor (TPS) with no luck in solving the problem.

I was having the exact same problem with my 92. I had the IAC cleaned, but a week later it started idling stange again. I asked around, and it turned out to be the oil pan gasket was bad, causing the IAC to be clogged. After I had that done, it worked fine!

Hey, what does IAC stand for? I think mine needs cleaned too. I'd clean it if I knew what it was. When I initially start my car for the day while it's cold it starts up no problem, but then kinda stumbles, then RPM increases just a little and then comes down and then it's fine after that. Maybe my IAC is clogging up. I don't know. I noticed when I got my car a month ago it had been overfilled by about a quart. I drained it to proper level, but maybe something happened while it was overfilled. I don't know. My pan gasket it fine, not leaking or anything, yet.