Exhaust is rattling

[Fvckbg]

wassup guys. A couple months ago installed a new cat back exhaust and it ran really good. No problems at all. I think it was made by spec D. Then just yesterday I installed a new catalytic converter (v tech) and my car sounded great. I can tell the difference in horsepower. But now when ever I press the gas hard I hear this rattling noise. It begins from 20 mph and it stops when it shifts gears them starts again but when I'm going like 65 or above it runs smooth. What's the problem? I looked it up and i saw answers that said "change octane fuel" or something like that. Or a loose hanger. Idk Also have a 98 civic ex

 

[Steven Johnson]

We need a little bit more info, but from the sounds of it, you're just hearing the new cat breaking in - or possibly didn't tighten something correctly.

 

[HeX]

Have you checked the heat shield beneath the car? Its possible that the new cat caused a slight enough alignment change to have lined something up too close to the shield.

 

[Joe Mason]

I agree with HeX. get under the car and wiggle the pipe around. See if it's making contact somewhere. Heat shields are where i would check first too.

 

[Fvckbg]

I agree with HeX. get under the car and wiggle the pipe around. See if it's making contact somewhere. Heat shields are where i would check first too.

I found out what it was. At least I think I do. I think it's the muffler vibrating a lot which is hitting the area that surrounds the muffler because I adjusted the hangers and now the noise isnt as loud as it was before.