Hissing noise when accelerating

[RustENutz]

Well I just got another Explorer. This one's my wifes DD, it's an 04' XLT with the 4.0. Super clean with 72k on it. Everything runs good, but two things bug me. First is the very slow reacting Drive By Wire, but I've read on that and will deal with it. The other thing I can't find anyone asking this question in my searches.

Anytime I put my foot on the gas there is a VERY loud hiss. At first I thought it was just the intake, but it's loudest from the driver's seat and we test drove 3 other 3rd Gen Explorers and none of them had a hissing like this. It's really annoying me.

So is there a problem or is it just noisy air entering the plastic plenum?

 

[corkey]

does it stumble at idle?
if it does, could be a vacuum line is loose or cracked,,
that could also explain the slow gas pedal action,

 

[SubLo]

I think I have this problem as well. After pouring over this forum, I initially suspected front bearings and/or differential. But the more I listen to it, the more it sounds like a hiss or perhaps even an very smooth exhaust leak. I've had exhaust leaks on other cars before and I know what they sound like - a little different here.

Like you, I get it only upon acceleration pretty much at any speed. Funny thing is if I put it in neutral and hit the gas, the noise is there but only for a second whereas it's constant when on the gas while in gear.

 

[dennism3]

Very much sounds like intake leak or vacuum.

 

[RustENutz]

I think I have this problem as well. After pouring over this forum, I initially suspected front bearings and/or differential. But the more I listen to it, the more it sounds like a hiss or perhaps even an very smooth exhaust leak. I've had exhaust leaks on other cars before and I know what they sound like - a little different here.

Like you, I get it only upon acceleration pretty much at any speed. Funny thing is if I put it in neutral and hit the gas, the noise is there but only for a second whereas it's constant when on the gas while in gear.

Exactly! Doesn't do it in neutral. It idles and runs perfect. No stumble or nothing. I agree....it almost sounds like a very smooth exhaust leak.

I've read elsewhere that when accelerating your intake pressure equalizes with outside pressure, so there wouldn't be any vacuum when on the throttle, so the noise wouldn't be a vacuum leak. Is this true? Also, how loud it is, it would have to be one hell of a vacuum leak! But it runs and idles fine. I've experienced vacuum leaks before on other vehicles and on my other Explorer, this has no symptoms of a leak.....but I've been wrong many times before!:

 

[Fox Fader]

I don't know what it is, but the X's 97 does it, my 05 does it some, the GF's 01 does it too.

 

[RustENutz]

I guess it just be the normal intake noise then. Probably transmits a lot of noise through that plastic intake.

 

[wth]

Our '02 EB with dual auto temp control has a vacuum hiss sound at part throttle when it's below freezing in the winter. Doesn't do it when outside air temp is above freezing. A slight change in gas pedal pressure will change the pitch of the sound when it's "hissing". Also sounds like it's behind the atc control and/or glove box area. Probably not even related to what you posters are looking for, but decided to post and see if it rings any bells to anyone.

 

[lynchy wa]

my 04 just had 105k service. the bloke who did it said mechanically all is good. i get the hiss when accellerating, but think it sounds a bit like turbo. nice to pretend sometimes.