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This is so strange. My 1996 V8 bird's airbox periodically makes a loud honk sound at idle, and up through mid throttle. I've taken the cover off, replaced the filter, and the honk is still there. The car does have a modified airbox per your article. I've had the hood open during a honk incident, and it took a wide open throttle rap to get it to quit. I've frightened children at curbside, as well as had a construction crew stop work in wonderment. I have cat back exhaust, but the honk out-sounds my tail pipes when it comes on. What could it be? It couldn't be the evap thing further below could it? If anyone has had this before, how did you stop it? thanks , edman:confused:
 

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This is so strange. My 1996 V8 bird's airbox periodically makes a loud honk sound at idle, and up through mid throttle. I've taken the cover off, replaced the filter, and the honk is still there. The car does have a modified airbox per your article. I've had the hood open during a honk incident, and it took a wide open throttle rap to get it to quit. I've frightened children at curbside, as well as had a construction crew stop work in wonderment. I have cat back exhaust, but the honk out-sounds my tail pipes when it comes on. What could it be? It couldn't be the evap thing further below could it? If anyone has had this before, how did you stop it? thanks , edman:confused:
Hiya, I just went through this. Mine sounded more like a fog horn than a honk, but I believe it's the same noise you're getting. Someone on this board gave me the idea. I shoved a small piece (couple inches long) of 3/8" fuel hose inside the big IAC tube hose and my noise went away. I hope it works for you too!
 

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Someone on this board gave me the idea. I shoved a small piece (couple inches long) of 3/8" fuel hose inside the big IAC tube hose and my noise went away. I hope it works for you too!
That would be me :D Glad it worked for you too.
 

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Yep, more like a fog horn

After reading the reply, I went out and pushed a found 1/4" piece of hose into the large iac hose and the fog horn sound was diminished in loudness.Thanks. So now I'll just buy a bit of 3/8" hose tomorrow and hope for an even better cure.But, the question about what causes this still exists. Does anyone know what the plastic box is supposed to do? Is it supposed to be hollow inside like mine is?
 

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After reading the reply, I went out and pushed a found 1/4" piece of hose into the large iac hose and the fog horn sound was diminished in loudness.Thanks. So now I'll just buy a bit of 3/8" hose tomorrow and hope for an even better cure.But, the question about what causes this still exists. Does anyone know what the plastic box is supposed to do? Is it supposed to be hollow inside like mine is?
Mine is hollow and I looked at one in the junkyard and it was hollow too. Funny thing about the cause - listen to this. I bought a brand new IAC valve and the noise got LOUDER, so I brought it back and got a second new IAC valve and had the same noise. So I haven't a clue what causes it. I think I saw master486 say a voltage fluctuation signal from the ECU controlling the IAC valve causes it, but that still doesn't tell me how to fix it. :zdunno:
 

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simple reason, its working like an oversized whistle. one air chamber is moving air at a different pitch and pace than the other. Remember the RECORDER you had to learn in middle school?? same principal.
 

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That's funny to read this because the exact same thing has been goin on in mine in the last few months. I hear the honking sound, tap on the gas, and it's gone. It would be nice to find an ACTUAL fix for this, but it's obviously nothing serious, or even minor aside from the sound. Of course, if anyone can give more insight or knowledge into this weird phenomenon, I would definitely appreciate it.
 

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simple solution would be a cold air kit.
Technically, the stock air box IS a cai. And does an aftermarket kit eliminate the IAC circuit (I don't think so)? And how exactly is that more simple than stuffing a small piece of 3/8" fuel line into the big pipe to reduce the hole size (which has been proven to work several times)?

I'm just saying...
 

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Technically, the stock air box IS a cai. And does an aftermarket kit eliminate the IAC circuit (I don't think so)? And how exactly is that more simple than stuffing a small piece of 3/8" fuel line into the big pipe to reduce the hole size (which has been proven to work several times)?

I'm just saying...
no kit can nor should eliminate the IAC...it's an integral part of the pcm's controls...so Big Ed H is way off in left field on this one
 

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I just have to say that I don't use that hollow box anymore and I don't have any issues at all. I did replace my IAC thinking that it was the cause of my stumble but as far as I can tell a vacuum leak caused by a bad brake booster was my problem.
 

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It's resonance in the inlet tube, being fed by the IAC.

The pieces that get cut off in the older cars' (the "violin case" article) are called "Helmholtz resonators", and are there to stop the resonance. :)

The 96 and up don't have that, so the silencer is supposed to kill what escapes. :)

Since we don't have that anymore, the fix is to change the intake; either length or flow will work. You have to kill the resonance to make the noise stop.

Restricting the IAC intake changed it; so that the noise got quieter. More restriction=less energy=quieter.

The small box on the IAC inlet is supposed to be full of foam; adding gas-compatible foam could fix it. A dirt-bike filter cover is an easy source of foam, and fairly cheap.

Try a different air filter, rebend the inlet tube, or something like that; you need to keep the IAC. :)

My IAC went out a month or so after my Black Cougar started making this noise; YMMV.
 

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It's resonance in the inlet tube, being fed by the IAC.

The pieces that get cut off in the older cars' (the "violin case" article) are called "Helmholtz resonators", and are there to stop the resonance. :)

The 96 and up don't have that, so the silencer is supposed to kill what escapes. :)

Since we don't have that anymore, the fix is to change the intake; either length or flow will work. You have to kill the resonance to make the noise stop.

Restricting the IAC intake changed it; so that the noise got quieter. More restriction=less energy=quieter.

The small box on the IAC inlet is supposed to be full of foam; adding gas-compatible foam could fix it. A dirt-bike filter cover is an easy source of foam, and fairly cheap.

Try a different air filter, rebend the inlet tube, or something like that; you need to keep the IAC. :)

My IAC went out a month or so after my Black Cougar started making this noise; YMMV.
Would a dirty filter cause the IAC to make the noise? I would assume so since you mentioned trying a different filter filter.
 

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It could; it's hard to say what changed to make it resonate.

Killing the resonance makes it go away; like hitting the throttle, for example.

The iac is opening and closing so as to make it worse (it's the driver supplying energy to the column of air); try checking to see if the little square box is empty. Adding foam to that is probably the best bet. Remember: Large pieces won't get sucked thru the IAC valve into the engine, right? :)

It would be funny if changing the filter out made it quit. :)
 

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I've had this exact problem for a while now. Also, if the honk / loud buzz happens when I'm pulling into the driveway, put it in park and don't hit the gas, the engine will idle all over the place.

Before I randomly start replacing parts of the vacuum system, anyone find exactly what the cause was? I just don't want to make the noise quieter, I want to get rid of it alltogether.
 

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I've had this exact problem for a while now. Also, if the honk / loud buzz happens when I'm pulling into the driveway, put it in park and don't hit the gas, the engine will idle all over the place.

Before I randomly start replacing parts of the vacuum system, anyone find exactly what the cause was? I just don't want to make the noise quieter, I want to get rid of it alltogether.
Mine used to honk like crazy when I first did my PI intake swap. The resonator box in my particular case had no foam in it (old age). What I did to eliminate mine rather than replace the foam was stick a small piece of vac line inside the big hose that feeds the IAC (sorta like that "beer can mod" the Mustang owners have been doing for years - gasket with a small hole). I'll try to get y'all a pic. See my posts above about this mod.

Anyways, every once in awhile with the car idling, I hear a light honking, but it's very seldom and I can hardly hear it now. In your particular case, if you have the idle jumping, you need to find a vacuum leak (I've seen them leak everywhere from the T fitting to the PCV valve to the canister lines). If you don't have a vac leak, try a new IAC valve.
 

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try a manual tranny mach 1 iac gasket it has different sized holes one small one large. worked for me runs like 9 bucks at ford
 

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I am glad I read this...

Some time ago I posted this...

As you can see and hear it sounds like the converter... Well I just got the car back today with new tranny converter and exhaust.. Guess what the hum is still there and I remembered reading this so I started to squeeze hoses.. So I look inside the box and no foam....

Can I buy a new box or do I have to find some foam??
 

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I found this air filter for one of my Stihl 046 chainsaws... It is gas safe and looks to be about the right size.. What do you all think???

 
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