[Christ]

My Civic did the IAC dance... it would rev to 1400RPM, then cut fuel and drop back to 775, then rev up, then drop, then rev up, then drop. I could let the clutch out in gear, and it would drive the car up to 1400 RPM, then cut fuel.

It's two things that cause it on the Civic - TPS and IACV. The IACV only works if the TPS is at or below 1%, to keep the engine idling. When the TPS gives the wrong signal, or the IACV isn't adjusted properly, the CAS (crank angle sensor) and TPS start talking to each other, and notice that the engine is getting up to unreasonable idle speeds. Once they get to the DFCO point (1400 RPM), the ECU reads the signal, cuts the fuel, and the engine speed drops.

Lather, rinse, repeat.

I don't think the Saturn has quite the same feedback loop, but the symptoms are close.

Also, the Civic, like most other cars, does increase idle when moving under no load, but not 2k.

I think I'm going to figure out why it's doing it in the first place before I start working magic on it.