The engine was degreased by a mechanic today. Engine idle is usually 700 rpm, but now it’s 2000+. I went ahead and wd-40′d all of the wire connections and throttle cables. I reset the ECM, no luck. I did disconnect the IAC, and the truck started and idle’d around 600 rpm. Reconnect the IAC and it’s back to 2k+. On the road, whatever speed I accelerate to, the engine holds that speed. Cruise control will not allow me to use the coast method to bring speed down. Only braking will slow it down.

Recent work completed…
1 year ago
IAC, battery, pcv valve, egr valve, knn cold air intake, starter, starter relay, battery cables, relay to starter cable.
Last week
plugs, wires, cap, rotor, tps, coil, fuel filter, oil and filter, tranny serviced.

I checked all of the fuses, all is fine.

I assume there is some water that has accumulated in one of the wires. I’m going to give it a day and see if the engine has magically fixed itself. Can I assume that because the engine idle comes down with the IAC disconnected that the IAC is the culprit? Or is there any other possibilites? ie. vacuum leak, idle control screw was jarred in the cleaning process, or what?

5.0 Ford
This engine is fuel injected. No carb. I tested the ohm resistence on the IAC and it is within range so that is not the issue. All vacuum lines appear to be connected properly. All fuses checked fine. It doesn’t appear that any connections had come undone.
Throttle Position Sensor failed because of the water.