2000BlkGtConvgobucks

Sounds kinda stupid and basic but do you have a k&n air filter? Mine has never hissed, but it does whistle at idle all the time. Where on the engine is the sound coming from? good luck

dkillgore

I was unable to tell where the sound was coming from. When I opened the hood all the other sounds of the car made it hard to hear it, but when I have the top up and the windows closed its pretty easy to hear when I'm sitting inside the car.

I do not have a K&N filter. It still has the stock air box.

scooter3

There is a vacuum hose coming from your IAC to a black box that then goes to your air intake. Pinch the hose between the black box and your air intake. If the sound goes away then that is what it is. Mine makes the same sound, but I have gotten used to it.

https://mustangforums.com/forum/4-6-...oes-it-do.html

MU71L4710N

mines got a hissing noise too but i can hear it comming from under the car but not when i pop the hood. i think mines an exhaust leak near my headers. are you able to pinpoint the hissing noise to any area of the car?

dkillgore

All I can pinpoint is that it is in the front of the car somewhere. I haven't had a chance to do any more testing. I'm heading to the Ford dealer in a few minutes here to finalize the financing and probably purchase a warranty plan, and will have them take a look at it and see what they can do. There are a few other problems with the car, but nothing major. (Rattle in the back of the car, probably a bad shock or something, and the foglights don't work).

dkillgore

I took the car to a Ford dealer to have some other work done, and I asked them to check into this issue also. They said it was a normal sound coming from the induction system on the car.

Thanks for the help anyways guys.

PROMETHEUS PRIME

That is true....you would most likely have a check engine light on if it was a vacuum leak. The plastic manifolds do make a hissing sound which is normal so most likely it is nothing to worry about. Enjoy the new car!