So, I've searched a few pages of threads on noises from rear of car with no luck. Car is an '89 Firebird 305 TBI. When I accelerate, I'm hearing this force of air sound from the rear of the car and it's extremely loud the harder I accelerate. I've had exhaust leaks before, but they never sounded like this. The sound goes away when you let off and it will not do it revving in park or neutral, so it's under load only.

Best way to describe it, it's as if there is an air hose back there being turned on 100 psi and blasting the underbody near the tank echoing off all the metal in the back of the car.

 

how does the car run? down on power at all? Does it have a catalytic converter? sounds like the exhaust is restricted somewhere. Partially plugged converter or one of the baffles in the muffler broke loose and turned sideways.

 

I didn't notice any power loss. It seemed to drive/accelerate the same as always. It just has this sound now all of a sudden which started yesterday. This car still has what I believe is the factory cat since it still has the air tube and my A.I.R. system is 100% there and functioning.

 

So, after the rain cleared out, I finally got around to investigating this closer. When the car is idling, I can hear a light air sound while leaning down to the tailpipe. If I rev the car, it does indeed make the same sound as accelerating. Now, I'm convinced it's exhaust, but whether it's the muffler or the cat, I won't know until tomorrow. I made an appointment at one of the exhaust shops. I was going to just unbolt the cat and "check" it out, but when I looked at the bolts and nuts, all I can make out are little nubs and blobs. It's rusted so bad, there's no way that's coming loose. So, I don't see any way to check anything myself very easily.

 

It's fixed! The exhaust shop put on a new primary pipe, muffler, and two new tails for 265.00. The muffler imploded.haha It was a mess inside. Also, I was fairly certain that my car should have had a single in dual out muffler and when I bought it, it had a single in single out. Even the muffler shop said the exhaust had been "messed" with too many times in the past. However, despite my concerns, the 24 year old cat is in perfect, clean working order. I was shocked, but it's fine. The car sounds more like a V8 now instead of a V6 and of course the force air sound is gone.

 

Guess i gotta goto the muffler shop lol my 88 305 tbi doing the same thing, thanks for posting

 

That wasn't to bad of a fix.