Hi there,

Can't help butt in, and I did read some of the blue wire mystery in Seein' the Blues so I've got to pose this one question just to get it unstuck out of my head: You have not at any time interchanged the IAC and TPS connectors or suspect someone else may have, have you?

The result would be inability to control idle if left that way, and once positioned correctly, the idle valve will go full open from the shorted motor driver transistor in the ECU, damaged when the TPS gets put on the idle motor socket.

If that's out in left field, I would start by doing your base idle setting - that blue white wire sets the idle valve opening nearly so but not closed when you ground it. You should get a short rev-up and settle back when you release the ground as the ECU puts it back in servo mode.

If you can, backprobe the orange wire at the TPS with a voltmeter to see it switch from +5 to ground when the throttle is closed. That's the same orange wire that gets interconnected to the ignition harness under the manifold.

I'm showing you below what the harness in my 84 looked like under the PVC sheathing so you know beauty is only skin deep sometimes. Still, I can't say rough idle is or has ever been pinned to a rotten harness - more likely a mechanical/fuel/air problem - such that you might want to take compression readings before doing more extensive work.