99 Explorer noise

I have a 99 Explorer, V-6. The air cleaner makes a constant horn-type noise after the engine warms up. What would cause this? It is VERY loud, like you are laying down on the horn.

Ratchet

Does it sound like this ?

I'm by no means an expert but I found this very helpful to ridding myself of a rather annoying noise coming from the IAC valve. http://www.explorerforum.com/forums/showthread.php?t=84220

It might be something different since this is a bit further up the intake from the aircleaner.

There's just so many great write ups, it's going to take me forever to get caught up

dogfriend, that is EXACTLY what it sounds like.

Runesai, I'll remove the IAC and clean it out like you described.

Thank you both for your help. I'll post after I clean the IAC to let yall know if I was successful or not.

Cleaning the felt pad inside the black plastic vent cover works for curing the foghorn noise on my truck. Some others have claimed that you need to replace the IAC, but cleaning the felt pads is much cheaper and doesn't take very long. I have found that it will work for about a year or until the weather starts to get hot.

I replaced my IAC with a new one to stop the noise but now my truck idles very rough, what happened

Maybe the IAC gasket is leaking. Did you replace it when you replaced the IAC valve?

If it isn't the IAC gasket, you could have a vacuum leak somewhere else (like a hose that fell off or is leaking). That will cause a rough idle.

Rough idle after replacing valve

Thanks for all the help, everything's great now, running great, and no more roaring, dummy us, the auto store gave us the wrong one and we put it on, took it back and got the right and WOW, working perfectly. You Guys are the best!!!