idle air control valve question. whait is duty cycle test?

Don't let the Ford dealer replace the IAC. It's so easy, a caveman can do it.
It is located on the upper plenum, near the throttle body, and is held by 2 small bolts with 8mm heads. Unplug it, remove the screws, make sure the gasket is not torn. Replace it with a new one. Any auto parts store should have it, and probably cheaper than the dealer. Save yourself at least $50. I bought one from Autozone for about $60.

I'm still not convinced that it is causing the problem. You see, duty cycle is simply a fancy term for "on/off". In other words, the computer turns it on when the engine is running rich, and off when it's running lean, thereby stabilizing the idle. Just like a thermostat controls temperature.

The question is: what is causing it to think it's running too rich or too lean?

Yes, I did do it myself! It didn't stall out again after it was at Ford, but within a week or so I had put the new valve in. It wasn't a lot of $ so I figured it couldn't hurt. At any rate, it's been running fine since. Who knows if that was the problem!

Now it may have a mystery trans leak that comes and goes and that the trans shop didn't see. I took it because a friend thought my pan was leaking, as it was wet. Shop said pan was fine, dipstick tube had leak. He fixed that and said he didn't see other leaks (but it was a pretty quick lookover-no reason at the time to suspect much else) . Butit still has had drips 3 times, that I know of, since then. Have to get my son (the only driver of it) to check that trans fluid more often!

I don't know if this will help, but I think there's an o-ring near the top of the dipstick (there's one on the oil dipstick, so I suppose there's one on the transmission dipstick, too.)

I could be way off, but this was the first time I saw an o-ring on a dipstick...