Why would the ECC want a high idle?

[MalcolmV8]

I've had my idle go very high twice today. Instead of 500rpm at idle in gear (auto tranny) it would be closer to 1000rpm and if I put it in neutral it would jump to about 1500rpm. It does not seem to quit doing that on its own. I tried driving around for a while and it would not go away. Just turning the truck off and back on corrects the issue and it does not do it anymore.

I tried unplugging the IAC while it was doing the high idle and the idle immediately dropped back down to normal. I plugged the IAC back in and it jumped right back up to 1500rpm. That leads me to believe the ECC is opening up the IAC but why? Simply turning the truck off and back on corrects the issue.

In the last two or three weeks it has done this twice and then today it did it to me two more times.

Any clues?

Thanks
Malcolm

[plowboy34]

I have no idea why it is doing that. Maybe if you would do what we use to call performing the idle learning strategy...you know...disconnect the battery for about 10 minutes then hook it back up. Let the truck idle in neutral for 3 minutes, then in gear for 3 minutes, then turn on A/C(if hooked up yet) for another 3 minutes. I know you probably already knew that just thought I would throw it out there. Sometimes those brains just need to be killed and then retaught how to do things. We use to have to do it quite often when I was at Ford.

[An11secranger]

I saw this a few times over the years. The cause, as I recall, was usually the air temp sensor. But it never threw the code.

[Blk87]

I had this problem for about a year. It ended up being a voltage problem to the computer. The voltage was to low. The ACT and ECT are a good start.