first of my truck is an 03, xlt 4.6 5-speed with 82,000 miles. Almost always when i come to a stop i can hear a faint humming that is coming from the engine compartment. There is no pattern or set way that this humming happens, it just comes and goes as it please when at idle. As soon as you put load on the motor it will go away. I got under the hood today and fired it up, nothing, gave it just a little throttle and sure enough here is this odd humming. It is coming from in the air intake. Any body have any ideas. Also while i was under there i noticed that the cable that is right next to the throttle cable is very loose, i am not sure what this cable goes to or if this could be part of my problem

 

the stock filter and air horn normally mufflle the noise... have you got an aftermarket filter, air horn or throttle plate installed--- they make the noise.

 

it is an aftermarket k&n cone filter but that has been on there forever and the noise is new. Also when you take the filter out the noise gets much louder.

 

Does it kinda sound like an owl hooting or goose honking?
If it sounds like either one of those-change the IAC valve.
JL

 

and since i am not very motor literate what is the IAC valve and where does it go and how much should one cost

 

Idle Air Control solenoid. It's on the upper part of the intake manifold,and replacements usually run around $35.
JL

 

Maybe this thread will help:

https://www.ford-trucks.com/forums/9...4-buzzing.html

 

Sounds like your mystery cable is for the cruise control. Someone correct me if I'm wrong.

 

Jayme

In the last 6 years, I've put 5 IAC valves on my 4.6, just to keep it starting up. Curiously, the most recent IAC had an assist spring located behind the piston. None of the previous valves had this.

Now, with the new valve, I get the loud humming that I think you have. I know it's the IAC, because after starting the truck, I can unplug the little 2 wire harness to the valve, and the humming stops immediately.

And, by the way, the last few valves I've picked up were $85.00 ea.

Dave

 

My original IACV had the spring you're speaking of. The new one I installed from Napa Auto Parts doesn't have a spring. No humming sound from either one of them.

 

Bird nest or cat in plenum..

 

Yes, IAC, Idle air control valve. I like the Motorcraft brand. Costs about the same as the Taiwan stuff in the aftermarket.

 

my f250 intake humming goes away if i remove the hose that goes to the valve cover from the intake. it creates a vacuum slowly and sucks air out of the intake into the valve cover. will the iac valve fix this or might i have bigger issues internally? the hose i am talking about is on the top of the drivers side valve cover and is attached to the lower nipple on the air intake toward the throttle body end of the assembly.

 

How snug did that hose fit the rubber boot on the intake duct work ? Maybe it's loose enough to have a air leak which may cause the noise. Possibly a small hose clamp can work, if you can get one on there.

Mine is pretty well gone. I did change back to the OEM filter instead of a K & N.

Dave

 

the hose fits very snug and is still very pliable. it is the stock intake with no modifications. i just don't understand why it creates a vacuum into the valve cover.