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Discussion Starter #1
Hi All,
Bullitt 2199 is doing well, but seems to have developed a "fog horn" like noise at certain times mainly at lower RPM's when it "caught just right". I suspect a bad IAC. I went to partsgeek and looked up the IAC number, but they are listing different numbers for the Bullitt.

Questions are...

1. Can there be different part numbers used on these cars and how can I be sure I am getting the right one for THIS specific car?

2. Should I use a Genuine Motorcraft Part? They are much more expensive...to the tune of about 60 bucks more. I can get a Standard Performance Brand IAC new for 40 bucks, or get the Motorcraft Genuine Part for close to 100 bucks.

I wanna treat the car right though and not have issues. That noise is actually kinda embarrassing at the worst possible times, so I wanna get rid of it. hehe :)

Thanks for any help you could provide.

Tim
 

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I think the difference in the part numbers is the plug position. As far as going with the motorcraft of after market. that is up to you and most people will not notice the difference. if it doesn't work as intended its really easy to replace so for a 60 buck difference I may try it..
 

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That is the correct Motorcraft part number. Also got mine from Amazon. Best price I found at the time.
 

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can try cleaning it first, sometimes that will do it. usually, as far as I know, there is no noise from the IAC, it makes the idle hang or search, but not any noise. I suppose if the gasket went bad it could or if the rubber hose is not hooked up properly or has a leak, it could cause a noise, but if all is sealed, should not. having you taken a stethoscope to it to make sure that is the noise?
 

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I've gottent that weird "fog horn" noise before.. kind of sounds like a loud tone or the brake is dragging? Mine happens randomly when starting from a stop, usually when letting out the clutch. It then goes away and doesn't come back. It's random.
 

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Discussion Starter #7
Thanks Guys. I'm still investigating this, but lots have reported that that IAC is notorious for making that "air horn" like sound. It sounds similar toif you blew across a moonshine bottle like they used to on Hee Haw...dang I'm showing how old I am there. It has a NASTY harmonic to it. I'll try cleaning the old one first and see if it goes away. I have also read others that said they cleaned theirs only to have it return some miles later and that they replaced it and it went it away. It seems as if this is an issue that not all these cars have...some do it and some don't.

I have also read that K&N drop in's (which this car has for the time being) are said to do this. It is annoying and ruins the sweet sound of the exhaust note. Unless you are really rocking hard and loud with the stereo it can even be heard over the stereo...it literally emanates through the car and you can almost feel it...it's dang annoying.

I'm going to do more inspecting and try to get it to do it under the hood. You have to "catch it" just right at a certain rpm and load to get it to do it, but it invariably does this when you get a look and then .... Hoooooooonnnnnk... they look away as if they're were saying "Oh Jeez, awesome car! What did he do to it!" hahahaha :shock: It's embarrassing.

I'm also doing clutch research now. It's got a noisy TOB, so I'm fixing to get into a major job on the lift with that one. This car has been well taken care of, but at 104K on the clock it's time for a few things to be done. The engine is like brand new, but there are a few things that need to be done to her.
 

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Fog horn IAC

Mine has had this sound since basically i got it home. Totaly random and stops just as you get the hood open. Thank you for locating this sound for me! I took my IAC off this morning cleaned it and it got louder. But I know what it is and have ordered a new one. Thanks a million!!!!!!!
 

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Discussion Starter #9 (Edited)
It seems as if this IAC uses a Diaphragm and a damper on it's internals. It's "believed" that the diaphragm cracking or bursting in a certain way does this. Also this type of IAC on Crown Vics exhibited this and Ford came out with a 92-44-4 TSB about a new redesigned inlet tube with a "muffler" that was supposed to stop this. Also F-150's and a couple of other cars have been noted to do this as well.

I suspect in the case of our Mustangs, the diaphragm is the issue here because cleaning it on these cars seems to make it louder, and this is actually a good test, because the unit is easy to get to, and it's not that hard really to clean it if you have have a garage or shop. I plan to go ahead and replace mine.
 

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Mine made that same sound before I replaced it. It was also hanging up sometimes around 2000 rpm's. Tried cleaning it but that didn't help. Replaced the IAC and haven't had any problems since.
 

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cleaned the one on my Bullitt when I had it several times with no adverse affects.worked fine, never had to replace it.

the cobra...same thing, cleaned it with no adverse affects. the snake does have a muffler in the middle of the line or hose coming off of the IAC. if you remove that, it makes a roaring noise, not a horn type of noise. why i say, if it has a break somewhere in it or not sealed, will make a noise but not sure it is what 02199 is describing.
 

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Mines acting up more frequently. Sounds like a humpback whale mating call.. is there a way to test the IAC Valve? Or just replace it.
 

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hi bullitt02199 you are correct that noise is definitly coming from the iac valve i have seen this symptom in many fords over the years that i have been servicing them go ahead and replace the valve dont bother cleaning it as it wont do any good the noise will just continue and as for oem or aftermarket the aftermarket one should be just fine as long as you get the right one
 

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My bullitt had that problem to I switch out the iac with a oem one it fixed the problem for a wile but still does it randome times but not as much as befor
 

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I think it's time for another IAC on 00205 as I am getting the searching idle.
 

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Glad yall posted up on this thread! 4439 has had this happen lately. As soon as i pull the camera up to take a video the noise goes away. Like the "humpback mating call" sound explanation. Mainly happens to me when the car is cold.
 

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Glad yall posted up on this thread! 4439 has had this happen lately. As soon as i pull the camera up to take a video the noise goes away. Like the "humpback mating call" sound explanation. Mainly happens to me when the car is cold.
Happended again to me this am at stoplight... very embarassing. Going to fix it for sure. Definatley a cold morning or within 20min of starting the motor.:rolleyes:
 
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