Magnaflow Cat problems on 540i?

[JohnnyE34]

I'm curious to know if anyone else running Magnaflow free-flow cats on their 540i's have had any issues along the line of throwing a "check engine" light.

I threw the light, took it into the stealer, and was told that along with a bad lambda sensor (which I will be replacing all four anyway since its about time), they believed my cats were insufficiant. Of course they wished to install oem cats to the tune of $2500. I've never heard of any issues with the Magnaflow cats, but wished to ask. Anyone?

 

[Abdoman]

A BMW tech told me that any aftermarket cats could cause the check engine light to throw. I'm not sure why, but it does make sense.

 

[Montana]

When I shopped around for my new cat, I too wanted to get an aftermarket. I talked to the operator at a "discount" shop from the internet and he said he wouldn't sell me one. He said do not buy one, buy the OEM and that he gets so many returns and stories about screw ups caused by after market cats. I heard that in a few other places too. Those parts are specifically designed with a certain amount of flow etc. Any deviation can cause excess blow-back or deviation from the overall design of the exhaust system. I'd say that the check engine light may not be a bad thing, it just might be saying, "hey I don't recognize what's going on here".

I sucked it up and paid my $900 for the OEM cat.

 

[JohnnyE34]

When I shopped around for my new cat, I too wanted to get an aftermarket. I talked to the operator at a "discount" shop from the internet and he said he wouldn't sell me one. He said do not buy one, buy the OEM and that he gets so many returns and stories about screw ups caused by after market cats. I heard that in a few other places too. Those parts are specifically designed with a certain amount of flow etc. Any deviation can cause excess blow-back or deviation from the overall design of the exhaust system. I'd say that the check engine light may not be a bad thing, it just might be saying, "hey I don't recognize what's going on here".

I sucked it up and paid my $900 for the OEM cat.

Very interesting. Hmm, well I am hearing a little this here and there from some boards, I also understand there is a Magnaflow oBDII cat out there that may be a little more fitting (as from a posting this morning from another guy).

And, I am assuming you replaced BOTH cats since there are two correct? Dealer wants $900 A PIECE for them, I have found some for a little less though here and there. We'll see what happens.

Thanks though. Any others have input?

 

[wood_e]

The only reason an aftermarket cat will throw a CE light is if there's an O2 sensor downstream from the cat.

 

[Montana]

i replaced only one at the time since it was the only one rattling. Yeah $900 each is right. Ouch.