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Throwing IAC CEL with 3L IAC, old and replacement

W

Wien_Sean

Hard-core CEG'er
Joined
Mar 22, 2003
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Location
Chicago, IL
I took a look though the old forums but I didn't find what I was looking for. I have a 98 SVT with a Full 3L swap (04 Taurus 3L) and I have been throwing a P1504 IAC circuit fault and a P1506 IAC overspeed error. I replaced the IAC with one that came off the low-millage 3L that SHOgoFast is using but it did not solve the problem. The seal looks good between where the IAC mounts and the IAC itself. Anyone else have this problem? I am sure there is a really simple answer, I just haven't found it.
 
Ok, while the connector is the same and it bolts up, but from our inspection on Saturday, we determined that they have different holes (3L IAC rectangular, 2.5 different) so do I have to modify a 2.5 or should I just try the 2.5 without modification? I think I can steal the one off of my mom's 2.5 to test.
 
not sure. i just know when we put a 3L iac on a ported 3l that is threw a cel .... which would have to be because of the differences in the iac.
 
Yeah that's what we were thinking, that the computer is looking for the voltage/reading of a 2.5 IAC and getting that of the 3.0 IAC and that's what's tripping the CEL. I have been told it should be using the 3.0 and if that's true it's time to check the wires again and also look for vacuum leaks.
 
So, now I have conflicting information. Brapple says 2.5, Pudmunkie says 3.0 IAC.

I guess you can try out the 2.5L one. The bolt holes are the same but the inlet for the 3.0 IAC is rectangular and the 2.5s are round. I suppose as long as the round holes are not obstructed by the 3.0 UIM then it should be fine. Worth a try, its free.
 
I am hoping it will just work. I will have about an hour or two of light before I have to get everything back together so I hope I can get home after work quickly.

Edit: I went out at lunch to check for wiring problems, but it looks fine as far as I can tell. I will have to take the UIM off to check the entire length of the wires.
 
Never heard of the IAC having to be different. My full 3L has a 3L IAC. Never had a code for it.
 
I didn't have enough light when I got home so it will have to wait till tomorrow. On my lunch break I will try to get over to Autozone to try out the one for a 2.5. It didn't help that all my metric bits are missing and all I have are standard sizes that are much to large for this task.
 
this is interesting to me, since for some unknown reason the place that sold me my 3l decided to remove the friggin IAC, so right now I've got my 2.5 one on it. we'll see how well it works I guess.

BTW brapple said to use the 2.5 IAC on a PORTED 3l, but you have a full 3l
 
I have been too busy to deal with tearing into this to find the cause of the CEL. I am certain that 3l IAC goes with the full 3l,it's probably just the wiring or a vacuum leak. I am thinking wiring since the idle dropped down to normal for a bit when it was raining the other day. I don't know but I am hoping to tear into it this weekend.
 
I am curious about the pipe/hose that come off the UIM right by or on the IAC mount. It was capped off with a screw in a hose. SHOgoFast and I took off the hose and capped it off properly, but I don't know what it is supposed to hook up to. Also did some tests tonight on the wires and one wire gets voltage, the other not. As per PurpleMystique's thread in troubleshooting, that is the way it is supposed to be. I am totally lost on further diagnostic tests. I did try unplugging the IAC and it made no different in idle if that says anything. So either the wiring is bad or PCM is looking for a 2.5 IAC and can't work with the 3.0.

Edit: Or the hose near IAC on the UIM needs to be connected to something.
 
How exactly do I test the wires? I kind of need detailed instructions because I don't really understand how this all works. I was able to get my hands on this image, if that helps anyone explain this.
106035338jy0.gif
 
Wien_Sean said:
I am curious about the pipe/hose that come off the UIM right by or on the IAC mount.
Click to expand...

What year is your 3.0? Here's my '01:

IMG_0664.jpg


I don't know of any vacuum hoses coming off of the UIM near the IAC valve. There are a couple below it on the back of the UIM, but those aren't for IAC, just EGR (among other things) and the brake booster.

Swazo said:
Are you saying that you don't have the IAC hose from the UIM connected to your air intake?
Click to expand...

The oval port UIM/throttle body uses a passageway in the UIM/throttlebody connection to provide air to the IAC valve instead of a separate hose. So if he has an oval port UIM, he won't have an IAC hose.
 
That's right, I forgot they mounted like that on the 3L UIM. I had a 3L UIM, but had the IAC area blocked off and the IAC tapped and ran externally of sorts. My bad.


Though, I wonder if he has it mounted backwards? Mosh has a pic of his '04 in his COP thread, and it's mounted backwards compared to your '01.
 
BACKWARDS!!! That would be so simple. Can we get a 100% confirmation on the correct orientation of the IAC on a 3L UIM. Wein_Sean's is mounted just as illustrated below.

Got this pic off of ebay for a junk yard motor.

ML9185-300.JPG


5de3_3.JPG


Swazo said:
That's right, I forgot they mounted like that on the 3L UIM. I had a 3L UIM, but had the IAC area blocked off and the IAC tapped and ran externally of sorts. My bad.


Though, I wonder if he has it mounted backwards? Mosh has a pic of his '04 in his COP thread, and it's mounted backwards compared to your '01.
Click to expand...
 
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