X1997J

Kind of a weird question but can some one tell me how many cats are on a 4.7 wj from California? I have a 2003 if it matters. Thanks.

dave1123

I believe there are 3. There is one on each bank and if you have a downstream converter underneath, it's not monitored.

X1997J

I'm guessing I need the third one (down stream) for smog purposes. It's starting to rattle pretty loud and needs to be replaced. Thanks for your reply.

dave1123

We cut the downstream one off my WJ to check it because we thought it was rattling but it turned out to be the muffler. The matrix was perfectly solid and clear so we welded it back on. Now I have a Flowmaster 50 on it LOL! Nice and mellow without being loud.

X1997J

Interesting. I hope its my muffler as well. I wanna put a super 10 on there lol. I'll have to get under there and kick the muffler see if its rattling.

X1997J

Also I just had the smog done the other day and it passed. I'm guessing if there was a bad cat it wouldn't pass smog?

dave1123

Actually, that third cat is just a "backup" deal to clean up anything that gets thru the other ones. That's why it's not monitored. The "duty" cats are small and might not catch everything.