I have a 94 Civic EX with a ractive muffler, headers, intake , and 2 1/4 in pipes, and when I accelerate when my car is cold, something rattles inside my pipes, you can hear it out the back. It almost sounds like when you take a piece of paper and blow on the edge. Is it the baffles or what. It almost completly stops when it is at normal temp. except for when I punch the accelerator. What the hell is this.

Also my brothers 97 Eclipse does this and he has borla exhaust.

 

Are you sure it's coming from inside your pipes. It may be the heat shield on top of the exhaust or the cat. When the car warms up, the metal on the heat sheild expands so that may be why you dont hear it anymore. This happened to my car so I just took the heatsheild off.

 

I do still have the heat sheild on my cat, I can never really tell where it is coming from since I am in the car. I'll try that thanks...........any other suggestions?

 

I removed the heat sheild on my cat and it stills makes that vibrating sound.
It is really annoying. Any suggestions.

Thanks

 

Check your header mount, I had a similar problem like yours. it turn out that the DC header mount broke off from the engine block. it looks not broken, get under the car and pull on the header. see if that's problem.

 

Did it only do it when it was cold.
It sure sounds like mine is coming from out of my muffler because I can here it echo off of cars, houses, etc... when I pass them.

 

You also might want to check the gaskets on the piping, if the pipes arent connected tight enough then air could be leaking out causing that noise as well. Have someone rev your motor a little while you check to see exactly where it is coming from.