I hear a hissing sound coming from the engine area when I'm driving and I give it gas. It sounds just like the air filter-breather is off, but it's not. I've checked it and it's snug and not broken or cracked. Does anyone else know what I could check. Any help is greatly appreciated.

you might have an intake manifold gasket leak, that or throttle body gasket leak.

Sounds like plenum gasket; numerous posts here. Quick check: open the butterfly on your intake with engine off. If you see oil inside, it's the plenum.

I checked inside the intake for oil but no luck. It looked clean inside there. Here's the thing now, I still hear air, and it's worse when you first start the truck. Craziest thing is the air is really loud, seems like the truck is loading up-bogging,all of a sudden there's a click, then a snap, as if something is closing shut. Engine runs good for a little while, but air sound is still audible. My question is what in the heck could be doing such a thing? Any help is very much appreciated. I'm about ready to run this thing over a cliff, or sale it.

check your exhaust system to the cat. if it is going out it will clogg and create back pressure. also look at the temp if it is heating up than to cat is going out.

My cat is empty, the guts were removed, it's just there for looks.

It's gotta be your throttle body gasket. Also check your vacuum hoses around the intake manifold, make sure nothing came off.

I AM NOW SEEING PEOPLE WHO WAS ABLE TO GET RID OF CAT. I looked what i thought was everywhere over 3 months with no luck on bypassing /tricking out O2 sensor could somone email me and braek it down.

I really couldn't advise you on how to trick the O2 sensor. My truck was already like this when I purchased it. However I have read that the pre Cat sensor was the only one that really had an effect with the PCM. So it's reading the exhaust before it ever passes through the CAT. I'm not really for sure, you should get another opinion.

I hear a hissing sound coming from the engine area when I'm driving and I give it gas. It sounds just like the air filter-breather is off, but it's not. I've checked it and it's snug and not broken or cracked. Does anyone else know what I could check. Any help is greatly appreciated.


Did you have any luck finding out what is causing this? I have a 99 ram 4X4 v8 5.2 and it sounds like I am having the same problem. Its been doing this for about 2 weeks now. When I am in traffic stopped I hear the engine hissing for the throttle body, if I put it in nuetral its idles faster, some times I even get a little backfire though the throtle body, and then a little hessitation. I have tuned it up, plugs, cap, wires, pcv, oil, air filter (Volant Air filter). Even checkedthe TSB index on performance issuse. I am at a loss here, hope you have figured this out. :headshake

Sorry to say that I've yet to figure it out myself. It just about has to be a vacuum leak of some sort I guess. Mine did it again yesterday when I first started my truck. It sounded like someone had an airhose under my hood. The engines idle went crazy, then the air sound stopped and my idle smoothed out somewhat. I'm at a loss as to what it is really. By the time I get out of the truck and pop the hood to listen where this is from it stops. Could be the TB sucking air as you say. I was telling someone that when I removed my Intake Air Temp. sensor that there was some oil on it. Maybe my plenum is leaking and causing this. But seems it would do it all the time?? And I've yet to have any pinging as described with the symptoms. Hope you have better luck than I have.

There is a quirk with the intake air hose. Make sure that your air intake hose if attached firmly or you will get the hissing and the loss of power and also a goofy idle. This info was passed to my by my old boss who has been a mechanic for 44 years. He also said to make sure all vacuum hoses are attached and no rips or tears in them, even a small hole in one of these hoses will have the same effect. Good luck guys.

"Mopar or no car is my motto!"