I bought an 07 F-150 XLT with the 4.6L V8 a few months back (except for a GPS unit, it is totally OEM). It currently has 8000 km's on it. A few thousand KM's back, I noticed that when my throttle hits a certain spot, it makes a weird hiss sound.. If i back off, or increase power the hiss goes away.. It's not linked to the RPM's because its happened anywhere from 1100 RPM to 2200RPM, it seems to be linked to how much gas it is getting. Im not sure if its affecting anything, but I find it REALLY annoying.. To me it's like nails on a blackboard.... Does anyone have any ideas or experianced it before?

 

Breather leak? My K&N did that for a bit. Not sure if it is the same sound, but, that is where I would check first.

Cheers

 

Yeah, it's hard to describe it.. It's like a high pitched whine/hiss but only when its getting a certain amount of fuel.. Would a breather leak only make noise when it's getting a certain amount of fuel? Ive considered bringing it into my dealer to look at, but I don't wanna bring it in and have him say there is nothing wrong with it...

 

Well, my four six, when I installed the K&N, I took it down the road and it made a horrible hissing/howling sound when I would let out of the gas. It stopped all on it's own.

If it does it CONSTANTLY, get someone to look at it. If you luck is like mine though, when you want it to do it, it won't. LMAO

I would just make sure all of your connections are tight with the air intake, and, the hoses on the side of it. Maybe that will solve your problem.

 

sounds almost like a vacuum leak. check all hoses going in and out of the intake tube. make sure you check both ends and that all connections are tight. if it is just a loose hose its not harmful, just annoying.

 

YUP YUP YUP, my 4.6 does the exact same thing, but it sounds OK to me. MID to HIGH range throttle will make it hiss a lot, but I think it's OK, and kinda sounds neat! I'm sure if it was an intake leak the mixture would be wrong and it would throw out a code.

 

I have an 07 F150 4.6l and it does the same thing. I am almost convinced it is coming from the throttle body somewhere. It only happens at a certain throttle position. My dealer changed the intake thinking that there could be a piece of slag in the casting making a whistling noise under certain conditions. That had no effect on the problem and when he drove an 08 4.6L it had the same noise. It was not quite as loud as my 07 but when I put the truck at the right speed and throttle setting I could hear it. Definitely not as loud but it was there. I would sure like to know what is causing it because I find it annoying. Reply if you find out anything.

 

Throttle Body replacement fixed my truck. Nothing visually wrong with the old one but it sounds very nice now.

 

is it high pitched sometimes and almost like a "hooting" at other times? If it is this is a common noise from the accesory drive belt during cold weather. I have found replacing the belt usually cures this issue.