A couple days ago my 04 developed a loud tick once it warmed up at idle. It goes away when throttle is applied and could only be heard from the bottom/wheel wells. With the hood popped you can't hear it above the motor.

After spending the last couple nights sick thinking I may need a second engine transplant I finally got up the nerve and crawled under today and when I wedge a breaker bar between the passenger catalytic converter and the frame the noise is almost completely gone.

I can't see anything that looks out of place, so what's the protocol for tracking down what it may be? Any ideas?

 

Bad cat? Mine rattled like mad when ceramic honeycomb came apart. Heat shield possible to

 

I was thinking maybe the cat was bad but I wasn't sure how bad they ticked/rattled. Pretty disappointing it's only like a year and a half old hi flow magnaflow.

 

sounds like a bad cat they will clank real loud at idle..

 

Awesome....I just started back college yesterday so I'm not were I can really do anything about it at the moment. I've also never had a cat go bad before. Can I just keep rattling and ticking for a while or will I mess something up? I tend to only drive about 20miles a week when I'm at school.

 

While looking around I came across this forum and they are discussing number of 02 sensors on certain D2's.

Discovery 2: Removing cats & O2 sensor - Page 2 - 4x4 Community Forum

This has me wondering if you live somewhere without emission test could you cut out the cats and have someone with the right computer change a setting so that there was no need for the trailing 02's? Or would you be just as well going with the anti-fouler method on the rear 02's and hope it didn't throw a code?