Catalytic converter swap on an 04 325ci

[JordanSD1]

I have a 2004 325ci with a 3.0 dropped in it. I just bought it less than a month ago off a private party "as is" with the check engine light on. They told me it needed an o2 sensor replaced. I drove it about 250 miles over the course of 2 weeks and noticed that it had a horrible loss of power. I mean... I had 318i before and it was much faster than this, lol! And above 3,000 rpm it would start to bog. But I'm an idiot and kept driving it and it went out on me while I was on the freeway doing 75mph. I pulled off to the side and let it sit for a minute. The engine never shut off but fluttered between 1500 and 2000 rpm. When I tried to give it gas it would bog again. So I drove it to a mechanic shop 2 miles away. It's a manual so I just let it idle and got it up to 3rd gear in idle and it made it there. The mechanic told me that it has bad catalytic converters and 2 of 4 o2 sensors are bad. I found a junk yard that will "swap" the catalytic converters for $400 in CA. Cause I guess it's illegal to sell used ones, I dunno, lol! But my real question is.... Since I have a 3.0 dropped in it, are the catalytic converters going to be diff? What model of a BMW should I look for to "swap" my converters out? Would any 3 series work? Thanks for your help guy's!!!

[dworthy]

Welcome to the Forum!

Well the exhaust system on the M54B30 is exactly the same for M54B25 and M54B20. So if the "guy" has one for a 325i or 330i, both will work/fit.

I am not from California so I don't know what is legal or not, but it wouldn't surprise me that they cannot resell emission parts.

[JordanSD1]

Thank you! I appreciate your help!

[328 Power 04]

It would be wise to check what ecu (or ecu programming) is running the engine, as well as what MAF and what size injectors. A mismatch of all of those can cause problems passing inspections as well.



Besides engine displacement, the 2.5 and 3.0 had different mass air flow sensor, different injectors, different intake manifold and throttle body, as well as different programming to run the engine.

[MarcoZandrini]

The first step in diagnosing a problem is to scan the DME for codes. Scan it and report back? Is the fuel pump original? When was the fuel filter last changed? The fuel pressure at the fuel rail has to be at least 50psi at all engine speeds. Part #2 in the link is the cap for the test valve.

http://www.realoem.com/bmw/enUS/show...diagId=13_0900

[dworthy]

Very true, OP you need to find out why the cat's went bad to begin with and fix that problem too. Normally the cat's are suppose to last the lifetime of the vehicle, so let's see about getting that fixed too.