Exhaust noise is driving me nuts, is it my cat?

[Bronze MFP]

I have this metallic fluttering/rattling sound when I accelerate between about 2000 and 4000 rpms, I think it's coming from the cat but i'm not sure. does anyone else have or had this problem? It's louder than my exhaust if you're listening outside the car.

[240marcuSX]

its probably the underside of the heat shield on the cat, at least thats what it was on mine before it eventually fell off one day, but since your cat is different than mine (s13) im not positive, get under there and look lazy!!

[Bronze MFP]

i'm pretty sure its not the headshields, i've banged around on all of them, and they seem like they are on there pretty tight. i'm just wondering if its my cat and not some part of my valvetrain or something bad like that.

[USDM240]

on the underside of your cat, there are braces that hold up the heat shield. those braces have square nuts built in to them. my guess is thats whats rattling. my friends S14 made the same exact noise.

[smokey240sx]

my cat is actually rattling and not the shield. I was told the material within the cat and rattle everytime the exhaust pressure is low (letting off the pedal.)

[Bronze MFP]

my cat is actually rattling and not the shield. I was told the material within the cat and rattle everytime the exhaust pressure is low (letting off the pedal.)

Thats what I think my car is doing too, except when I accelerate.

[tonynalli]

heres an idea, take off the cat and gut it, then you wont have that problem

[Tyger]

I have this metallic fluttering/rattling sound when I accelerate between about 2000 and 4000 rpms, I think it's coming from the cat but i'm not sure. does anyone else have or had this problem? It's louder than my exhaust if you're listening outside the car.

Wow!!! And this whole time I thought my car was just a pile! LMAO I have the same problem and I think if we just change the Cat along with the exhaust we will eliminate the problem in itself. I spent 5 hours the other day taking everything apart trying to get rid of that sound only to have it come back even louder! LOL Off to the muffler shop I go!

[metalsyth]

Yeah to me that sound like the inside of the Cat has busted and depending on your emission testing you can gut it or the other replacement is to replace the Cat altogether those are the only real ways to fix that.

[sunnys14]

i had a rattle at take off. it was really annoying, so i found out it was the heatshield on my cat. i just pryed it off with a screw driver

[240Titan]

my next door neighbors 98 240 had the same problem a while back... he changed the screwed up cat and it went away

[SidewaysAndHighways]

I have a 90 240 that I just put a 2.5" exhaust on from the header back into a JCW muffler and after 3k rpms I get the same noise really bad. I think that it is because I have no cat If someone else finds another answer please tell me.

[ddgsxr504]

Ok here is 411 for everyone with an S14. The noise you hear is the heat shields. There is the one that is built onto/around the CAT. There is one that is bolted to the chassis above the CAT. There is also one that is bolted to the chassis by the firewall/bellhousing above the stock downpipe. All of these need to be removed! Even if the bolts are tight the shields are only bolted down in the certain areas which makes the rest of the shield rattle from the vibrations of the motor. This is espcially true when you start putting mods on your car. I would ditch the cat and get an aftermarket one or go the route I did and get a 2.5" or 3" test pipe.

[halfassracing]

try leaving all the heat sheilds off. if thats no good then cats no good