Originally Posted by Jafro
Man... when it idles back and forth like that, it's getting the wrong signal. It sounds to me like you swapped your IAT sensor harness and your IACV harness. They have the same plugs. It causes exactly that, but usually you get a check engine light with a code 14.
Something tells me you've done more maintenance to this car than you're telling us. But if it just started doing all this by itself, I've heard of stranger things happening. I know someone that did the thing I listed above to someone else as a practical joke. Wasn't very funny.
This happened to me, I had the connectors switched or so I think. I'm still working on the car, but I'm pretty sure that's what the problem was. What colors are the wires that go to each connector on the harness? If someone can check for sure it would set my mind at ease. I still haven't fuigured this one out because no matter how I try to reset the code it still comes back after a few seconds after turning on the ignition.