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Old 10-12-2010, 01:44 PM   #1
m5racer
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Blown Cat....preformance exhaust.....what to do?

hello all.

I have an E39 01 M5 and it has a blown Catalytic converter. Im having some power loss issues and a cold idol issue and im figuring this is prob effecting the performance of the car since its slow as ass now.

Would would be my best option is replacing the cat? Factory replacement is out of the question since i was quoted 4000+ to replace it. . Should i go High flow, remove the cats completely (heard that the loss of back pressure from doing this will result in a loss of power) or is there some sort of oe style replacement.

I'm also looking in the market for a full cat-back exhaust system. I like the tubi (but they are hella expensive), but wanted to know what other people run and which brands I should consider (my daily driver is an A4 so I dont know much about BMW preformance) I already have 2 magnaflow mufflers in the back, and I want something that sounds more agressive + sexy


Some help in this matter would be greatly appreciated.


* Im also looking for a shop that has a lot of experience with M5's or M's in general. This car is my baby and I only want the best for her. Something close, or semi close to Toronto
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Old 10-12-2010, 03:47 PM   #2
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How did you diagnose bad cats? Is the check engine light on? If it is what codes did it set? You could also have a bad camshaft position sensor which would give you similar symptoms. It could also be the MAF(s) which is a common E39 problem.
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Old 10-12-2010, 04:20 PM   #3
m5racer
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Quote:
Originally Posted by marek View Post
How did you diagnose bad cats? Is the check engine light on? If it is what codes did it set? You could also have a bad camshaft position sensor which would give you similar symptoms. It could also be the MAF(s) which is a common E39 problem.
Was told they were blown during my last e-test (may 2010), it had a code for the cat. Pretty sure it was the right side
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Old 10-12-2010, 04:39 PM   #4
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Originally Posted by m5racer View Post
Was told they were blown during my last e-test (may 2010), it had a code for the cat. Pretty sure it was the right side
I would take it to someone to pull all the codes, as a bad cam position sensor will also throw a similar code depending on which bank it is. You don't want to start blowing money on parts that don't really need to be changed out.
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Old 10-12-2010, 04:42 PM   #5
m5racer
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Thanks Marek
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Old 10-12-2010, 04:45 PM   #6
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Thanks Marek
The occasional M5 e39 would come into the dealer with cat problems back when...So it is possible one or both are gone. But be for certain this is the case as mentioned it is costly. Also, make sure the aftermarket are legit as you'd hate to spend say 1500-2000 and then find out it won't pass emissions. However, there are ways around that too!!
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Old 10-12-2010, 04:52 PM   #7
m5racer
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The occasional M5 e39 would come into the dealer with cat problems back when...So it is possible one or both are gone. But be for certain this is the case as mentioned it is costly. Also, make sure the aftermarket are legit as you'd hate to spend say 1500-2000 and then find out it won't pass emissions. However, there are ways around that too!!
Ya, when I did my e-test i was quoted 4400 parts + labor for the right side cat (OEM Replacement). And if i could tune the car to run nicely with no cats that would be great too

Ceeker, have you ever seen these cars idol like this

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Old 10-12-2010, 09:34 PM   #8
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Just remember running without cats is illegal. So if you do decide to go that route have someone make you a decoy. That way if you ever get pulled over and cops check under the car they won't suspect a thing.

I know one guy that got two aftermarket cats for his 740i $500 for both. But that was a while ago. Eurostyle is parting out an M5 as we speak, message him and buy the used ones
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Old 10-12-2010, 09:43 PM   #9
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if you dont need an e-test, why you fixing this man?
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Old 10-12-2010, 10:13 PM   #10
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You should check and make sure this is what you need before you spend that kind of $$$...Keep in mind that cheap aftermarket cats are good for about 1-2 years, and then they fail Etest again. Finding used ones can be hard, but just so happens that i am parting one right now, cats should be off tomorrow!
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