Idle air control valve question. Whait is duty cycle test?

Tiny
WHITALL
  • MEMBER
  • FORD TAURUS
Ford couldn't find any definite reason for why my 2001 Taurus DOHC, 85k miles had two evenings (2 weeks apart) that it stalled when placed into drive, and once died at a light (but restarted). It was fine for them.

They road tested it (I assume!) Did star test, pid moniter, fuel pressure was 53 psi, fuel trim and baro pids, baro 156--all ok. I don't know what all that is.

Tested the IAC duty cycle and got 54% which they say is High. They suspect it is beginning to fail. Also suggest a fuel filter.

SO, it the IAC a likely suspect and what should it cost to repair? This is the DOHC, pain in the butt, engine. The part is about $90 and they want $50 labor--1/2 hour.

They claim it looks pretty good otherwise, didn't notice any tranny issues and gave me the cheapest price (out of 3) for a power steering rack!
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Tuesday, July 24th, 2007 AT 9:03 PM

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Tiny
BLM
  • MEMBER
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?
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Wednesday, September 26th, 2007 AT 7:11 AM
Tiny
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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!
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Thursday, September 27th, 2007 AT 11:03 AM
Tiny
BLM
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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.
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Friday, September 28th, 2007 AT 8:50 PM

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