[stefanv]

Thanks all, for the replies above.

I'm pretty sure the IAC isn't the problem, since the high idle even happens during later gear changes, not just immediately after a kill-and-restart. The ECU would have reset it to where it wants it long before that.

I don't think the ECU controls the lights, but the same switch position that shuts off the ECU shuts off the (daytime) lights.

The kill switch is wired to a normally-closed relay, whose contacts are in series with the +12V feed to the fuel injectors (very easy to wire in, as my circuit just plugs into the dedicated fuel injector fuse's slot). The ECU isn't "aware" of this mod at all. As far as it's concerned, the engine just stalled for no apparent reason.

I guess I could kill the power to the ECU instead, but as you've mentioned, that doesn't solve the airbag problem. It also means that Torque will disconnect from the OBDII port, since the ECU will have vanished. I also wonder how the ECU would respond to waking up in a car that is already in motion.

One other data point. When the car is in this high idle state, if I stop at a light and don't turn the engine off, the idle eventually settles down, dropping to about 1000rpm (which is still a bit fast) after about 30 seconds of high revs (which feels like forever, and burns a lot of gas).