About 2 weeks ago I began hearing a rattling sound that sounded as those it was coming from my exhaust. At first I believed that the rattling was due to a lose exhaust, but that wasn't it. I chatted with some buddies and they said it could your catalytic converter.

Any advise on what else it could be?

 

Do you have a cat CEL code?

Have you ruled out a rattling exhaust heat shield?

 

No I haven't. I am fairly new with cars, but learning fast. What is a "cat CEL code"?

 

P0420 is a CEL code that generally indicates that the catalytic converter is bad.

 

incase you were wondering CEL means Check Engine Light

 

If your car has a CEL (check engine light) you should be able to see if when your car is turned on. the light will be on your instrument cluster. It's an orange light with a little picture of an engine on it.

If you have a CEL you can get it read for free at many auto parts stores.

I had a rattle years back on my '98 EX coupe (and have heard of it on other Civics as well). Seems pretty common for the catalytic converter heat shield to rust out and one of the halves to rattle like crazy.

On the EX the catalytic converter is about dead center underneath your car. On the DX it's under the hood though. The cat is a piece of the exhaust system.

So if you open your hood and look at the front of the engine you'll see the exhaust manifold aka. header coming off the front and dipping under the engine and toward the back of the car. On the DX the catalytic converter is a thick section of the exhaust pipe right underneath the exhaust manifold. You might be able to see a wire for an oxygen sensor going down to it as well.

Don't touch the exhaust parts if the engine has been running recently btw. It gets very hot!

The heat shield is just the vented metal cover around the catalytic converter.