Very loud

[steadyhand]

I have a very loud humming noise coming from behind the front passenger side headlight. At first I thought nothing about it, but it seems to have gotten louder. I can hear it inside the truck now even when the radio is on.

I finally got out and popped the hood and I was surprised at how loud it was.

It doesn't sound like a vibration at all. It sounds more like a high pressure hum or like the sound of an electric motor spinning. It is not coming from engine, I am certain of that. If I put my ear to the front grill by the headlight it seems loudest. I can put my hand on the air breather and push hard and it will just slightly quiet the noise, but not much.

It also seems like my fuel mileage has dropped a lot compared to when I got it. It used to be quite decent on fuel considering it is a 5.0. I always drive it very conservatively, rarely getting over 2200 rpm's even when accellerating. Now however I am constantly at the pump.

It doesn't smoke so despite the drop in MPG it doesn't seem to be burning rich.

Is there some type of canister or hoses behind the grill area or maybe under the breather that could be causing this noise I'm hearing?

 

[JDraper]

Check your air filter to see if it's clogged.

 

[Turdle]

The noise is actually coming from downstream of the air box, the IAC valve is dirty. When this happens the seal inside becomes a "reed" and vibrates as air moves across it.

To verify this, while engine is "humming" disconnect the IAC valve electrical connector-the noise will go right away.

Follow the IAC cleaning "how to thread" located on this forum. Pay real close attention to the inside seal around the internal hole.

 

[steadyhand]

I have a brand new air filter from when I did a recent tune-up. I didn't think about the IAC, but now that you mention it the engine does seem to be developing a slight vibration as well. It is random and doesn't always do it, but it could be the cause for that also. I'm going to take a look at it and clean it anyway. I'll update this and hopefully that is the problem.