Cat went bad
 

Last week it sounded like i had about a handful of bolts and nuts loose rattling under the car. i lived w/it.

now it sounds like about 10 bucks worth of nuts and bolts under there. there's no way i'm going to/can shell out the 2k for what bmw offers. so i'm really looking into an aftermarket cat to put on there.

my first thought is take it off, bore it out and see if the CEL comes on. if it does then it's new cat time. if not then see how long it runs.

i'm really thinking about a magnaflow cat which seems to be pretty well built and should work well? the problem is that magnaflow gives one number for our car, jeg's gives another, and summit still another number, but all of the sizes seem to be the same.

i DO NOT want to have this awesome fun to drive car sound like a honda, or some riced out stuff. I really don't want to be any louder than stock (a little is ok, anymore won't fly).

any help is greatly appreciated.

Dave
ps.
the kicker is that the pipes, welds, etc themselves (being a 99) really look good and besides the sounds from the cat, look like the whole system has lots of life still left in it.

I'm in the same boat as you Dave. I need to do something with my cat and not sure what to do.

Not trying to hi-jack the thread, but how much louder does the sound of an empty cat make the exhaust?

it's a bit louder... FYI, I have a perfect mid-section with a good cat just sitting in the garage. It's OBD1, so it would need a second hole and bung for the post cat o2 sensor. It should bolt right up otherwise. I'd be willing to take any offer for it, but shipping would be costly...

I look at it like this as far as noise reduction:

Cat: 30%
Resonator: 30%
Muffler: 30%

10% of your exhaust noise is left to exit the car so if you remove the cat or bore it out you will have 40% exhaust noise and it will be louder then you want. Just my thoughts

heres what you should do (and what ive been told from my mechanic friend that worked as a mechanic in the BMW service dept. here in cali) A used OEM cat will alway be better than a New aftermarket cat.

My advice would be to look on craigslist for someone that is parting out a 318, 318i, 318is (there are many out there) and buy it used (although in many states is "illegal")

thats what i did. and my check engine light went off all on its own. didn't even have to take it in to get the light reset.

good luck.

if you gut the cat, I seen posts about using spark plug extenders to move the second o2 sensor further out of the exhaust stream supposed to keep the cel from lighting up..

a guy that i work with mentioned that
 

It looks like a metal elbow. o2 sensor in one end, and the other end into the bung on the exhaust. easy peazy.

All i really need to do is make sure the thread is right for it. i think they are only like 10-15 bucks.

I'm still trying to figure out how a used oem cat is better than a new aftermarket.

thanks guys for all your help.
Dave

I still have this if anybody needs it:

http://www.318ti.org/forum/showthread.php?t=31554

aftermarket cats always throw CELs on BMWs, unless the OEM cat has 200k+ miles on it there should be plenty of life left in it

www.blunttech.com Steve can hook you up with an aftermarket for about 425 I think is what he quoted me.

contact 3.2ti in FL when he removes my old 1999 M44 motor the cat will (I'm guessing) be for sale. It was new, zero miles in 2007/8 and has about 20k miles on it.

Hey I have a 98' 318ti with a m44 motor that has a bad cat. I bought the car used and the kid put in an after market cat now the check engine lights keep coming on. I would like to replace it with an OEM cat for my car, will your cat fit my car and better yet is it still available. Thanks in advance.

I ended up with a magnaflow universal
 

so far so good! The sound is good, and it certainly is 'blocked' up like my oem was.

I think it was 74 from amazon (but summit price matched it) but it's only legal for 49 states. I'm in Pittsburgh so it doesn't matter.

The oem on mine was trashed. it was the problem. Unfortunately i'm only going to get another week or so out of driving before i park it for the winter.

In my opinion at 74 for the cat plus ~80 to install, i can do this every year for the next few if need be and still have more money in my pocket vs. an oem.

I'll let you know how it goes.

Dave

My cat went out around 148K on my '96 base. My shop assured me the replacement would pass state emissions test. New cat placed and "check engine" light came on again. New O2 sensors...light went off. 200 miles later, light came on again. Hit a deer and took it to the shop and they reset the maintenance lights. 1 month goes by and its time for emissions check. Fingers are crossed, emissions passed. 5 miles later, light came back on. 2 yrs until I need emissions again. Whew!

Do NOT do after market!

I like many others did not want to spend the 1800 (is that how much) on an OEM CAT. So I found a bolt on after market cat from my local auto parts store. After ONE tank of gas the thing started to rattle, then it threw a light. I was forced to take it off and return it. I decided to go for it and buy and OEM one. That was about a year ago, runs just fine. A word of warning... there is about an 800 core charge for the OEM cat, so if you do end up going after market.. hang onto your oem cat, just in case you decide to get the oem cat at a later date.