Hey Out there!!!! My 93 DeVille has a pretty noticable rattle coming from underneath the passenger side of the the car. The rattle is only heard while the car is in Idle. Also, the rattle doesn't seem to be very consistent. It happens all the time but it will vary in volume, and is more likely to happen while the enginge is cool, though it is also heard while the engine is warm.

Does anyone have any insight?????

The brick inside the catalytic converter is loose. The converter is failed. With the engine off reach under the car and pound on the cat with a rubber mallet. See if it rattles. If so, then this is the problem likely.

I agree with KC....

...my '93 DeVille was doing the same exact thing (well, among many other things0 and it WAS the cat.... pita... but soo nice now that it is fixed.....

... I would get a new cat in there ASAP... you can blow the enigne if back pressure gets too high...

Cool guys thanks. How much did you pay to have it replaced?