PDA

View Full Version : Loud ass hissing noise


tweiss3
06-27-2011, 07:53 PM
91 Naturally Aspirated

Drove and sounded fine on the way to work this morning and at lunch. On the way home however, I hear a loud ass hissing noise (can't figure where, tried for about an hour). I also have no power. It still feels smooth, just no fucking power.

I have the factory emissions in place. Any ideas?

Dzire
06-27-2011, 08:25 PM
might be a bad vacuum leak somewhere

tweiss3
06-27-2011, 08:38 PM
where would i look for the vac leak? It does sound like one, but idles fine.

Pete_89T2
06-27-2011, 08:51 PM
A vacuum leak big enough to be heard would result in a crappy idle. Where in the band is the car lacking in power - top end or everywhere? Did the S5 NAs use pressure from the air pump to operate aux ports/VDI; maybe the hiss is from an air pump plumbing leak?

tweiss3
06-27-2011, 08:56 PM
It may be airpump. I do believe it was used for aux port operation. I'll see if i can figure out where it could come from and check it tomorrow

tyler
06-27-2011, 08:59 PM
Can it be heard while reving in neutral?

tweiss3
06-28-2011, 05:30 AM
yes

tyler
06-28-2011, 07:44 PM
Is this noise heard at all times or under load?

tweiss3
06-28-2011, 08:14 PM
yes, its there all the time

tweiss3
07-01-2011, 05:39 PM
It appears to be coming from the header to downpipe connection? Could my cat have melted and blocked cause it feels like anything above 3k is where the lag is. I may try to pull it tomorrow morning and see if it looks free and clear.

I tested all the variable intake valves and went over all pressure and vacuum hoses, and they all worked and were in good condition.

NoDOHC
07-01-2011, 10:04 PM
Melted cat is a good possibility, the best theory I have heard so far.

tweiss3
07-02-2011, 03:55 PM
It was the cat, i got pictures to post later. I gutted it and put it back in, im up and running again like ot should be

tweiss3
07-05-2011, 06:37 PM
pulled the cat and saw it wasn't being a good girl
http://i44.photobucket.com/albums/f49/thomasweiss3/91%20FC%20NA/badkitty.jpg

so i punished it
http://i44.photobucket.com/albums/f49/thomasweiss3/91%20FC%20NA/punishedkitty.jpg

tyler
07-05-2011, 09:37 PM
Haha nice...I almost gutted my cat but I don't wana buy another for echeck

NoDOHC
07-05-2011, 11:21 PM
Yeah, I have seen the plugged cat before (several times) unfortunately, I had to replace it (emissions). I think that the guts may have fallen out lately though, as I noticed the car being a little louder. If I don't look, then I don't know....

Glad you found the issue!