You can get a generic catalytic converter installed around here (Los Angeles) for $100-$125 if you shop around and call the mom & pop muffler shops. Can't really speak for their longevity compared to OEM, but they will get you through smog if that's all you happen to need and I've never had one go bad within at least the next smog test.
Having said that, XJs need a certain amount of backpressure to develop power. Gutting the cat will help to reduce that backpressure - and it'll also cause the oxygen sensors to set the fuel mixture way out of spec, which will affect performance and fuel economy. I know you're out of cash until Friday, so just drive it that way for few days then replace it ASAP. In the long run, it's a false economy to disable it unless you bypass the
entire exhaust emissions system.
To answer your original questions:
Switch1625 said:
was told to check the catalytic convertor to see if it rattles when you knock it, and it does.
This is usually the sign of a shot cat. Technically you shouldn't hit it - just grab it (when cold) and shake it a bit. Hitting it could conceivably break the internal elements, but in your case it sounds like this had already happened.
So someone told me i could remove it, and clean it out with a broom stick, so i think i got the cat off,
This is essentially correct - but how did you remove it? Every XJ I've ever seen had it welded in place downstream of the exhaust downpipe but ahead of the muffler. Was your just clamped in?
and looking inside, halfway thorugh is like an air filter type thing, and there is some white thing laying in the cat. What is this?
The thing that looked like an air filter or wire mesh is typically just a debris screen to catch any metal from the white thing - which is the (usually) platinum/ceramic element that superheats to vapourise the 'bad' emissions as they exit. Depending on how your cat was constructed, there may be a mesh screen at either end of it.
Find a shop that can do it cheap with a generic cat and replace it the first chance you get.
