95 Bronco 5.8 high idle problems

[johnocean]

Well, I've posted this problem at a few places with no luck. Maybe there is a seasoned technician here that knows the answer.

Out of the blue, my pampered, well-maintained '95 351 W has an idle issue. This began on July 2, 2007. As a side note, this is the day the weather in north Fulton (GA) changed dramatically from hot dry days, to cloudy wet days.

Continuing, the first start of the day goes like this. Normal crank. Motor idles at about 750 rpm for about 5 seconds. It then takes off to 1500 rpm for 1 to 2 minutes. CEL flashes 4 times. It then drives and idles absolutely normal. Park it for 20-30 minutes (motor is already warm), same thing happens.

I've had it in 2 shops. The last one was a Ford dealer. Both shops spent a good deal of time on it. Same thing from both shops. No codes. The Ford dealer tech (and I spent time with him in the service bay) told me the EEC was resetting after the idle runup, therefore no codes. The next step is to drop it off for 2 days, and hook it up to a "breaker box" to test all the circuits individually. This will cost a boatload of money.

I've already replaced the IACV, cleaned the MAFS, reset the EEC twice, checked for vacuum leaks, run the self test, and two trips to shop.

Here's the kicker. Today, Saturday, was warm and dry. First start of the day still had the high idle. However, the next 2 starts were normal.

Has anyone run across this problem before?