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AZBMW Forums › Model Specific Discussion › 5-8 Series › Misfire and cat issue...perhaps
Misfire and cat issue...perhaps
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bmw325i
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PostPosted: Tue Jun 10, 2014 6:18 pm
Post subject: Misfire and cat issue...perhaps

Hi,


BMW E39 540i production date 6/96, 175k miles. For the past 2 weeks I have been running into the check engine light popping up, after getting scans it shows cylinder 7 misfire and also P0430 along with it. I swapped coils and replaced spark plugs to no fixing it. Is it possible the cat is out on bank 2 and thus kicking the misfire code as well.

My pre cat oxygen sensors are brand new, post cat replaced with used lower mileage ones. Is it worth checking them as well or the cat is shot and needs replacement. Thanks

P.S. And how convenient this month my car is due for emissions.
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bastarde38
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PostPosted: Tue Jun 10, 2014 6:41 pm
Post subject: Re: Misfire and cat issue...perhaps

Is it a constant misfire? or intermittent? if your cat was bad you would probably have more than one cylinder setting a fault. but yes it is possible thats whats happening. replace your post-cat o2s with new to know for sure. they are what set efficiency faults.

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ccc13
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PostPosted: Tue Jun 10, 2014 7:02 pm
Post subject: Re: Misfire and cat issue...perhaps

When mine (6/96 also) started clogging the cats, it got progressively worse and worse. The CEL would intermittently pop up with misfires, then noticeable misfires would happen, then it ran like an absolute bag of ass and refused to rev. I swapped plugs and coils to no avail. Then the cat efficiency codes finally came. This all happened over the course of maybe 2 weeks.

Have the cats been replaced before? How about the CCV? I agree with bastard's suggestion; the M62 does like to clog those darned emission devices.
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bmw325i
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PostPosted: Tue Jun 10, 2014 7:34 pm
Post subject: Re: Misfire and cat issue...perhaps

CCV was replaced 2 years ago. Never had misfires up until now. I am not sure if cats were ever replaced in the past, is there a way i can tell looking at the cats, I know they are OEM since they have the BMW logo on them.

The strange thing is that its only cylinder 7. The first time it happened the car was shaking and lost power when i swapped the coils and replaced the spark plugs when the misfire and bank 2 cat efficiency below threshold pop up car is not shaking at all, albeit it doesn't have that get and go power. I hope that helps.

I am looking at cats online already just thinking ahead i guess.
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ccc13
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PostPosted: Wed Jun 11, 2014 1:02 pm
Post subject: Re: Misfire and cat issue...perhaps

FWIW, I replaced mine with some Magnaflows for like $250 and all was well after that. If it is your cats, that's a possible avenue to take. Also sounded a lot better after that too.

If the cats are REALLY clogged and the car misfires and shakes, you can pull the pre-cat O2 sensors out. The car then reverts to a default fuel/spark map, and the exhaust has a place to go. You'll throw some codes and it's loud as hell, but if the misfires stop and you get power back, you've found the problem. It doesn't sound like yours are that bad though, if it's even the cats.

Really strange that it's only the single cylinder, though. Mine was 5-8 and "random misfire" as well.
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bmw325i
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PostPosted: Thu Jun 12, 2014 10:23 am
Post subject: Re: Misfire and cat issue...perhaps

I am going to switch the post cat O2 sensor on bank 2 and see if there is any difference.

Anybody know a reasonably priced exhaust shop that can put in an aftermarket cat if i end up going that route. Thanks in advance.
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bmw325i
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PostPosted: Thu Jun 12, 2014 12:27 pm
Post subject: Re: Misfire and cat issue...perhaps

ccc13 wrote:
FWIW, I replaced mine with some Magnaflows for like $250 and all was well after that. If it is your cats, that's a possible avenue to take. Also sounded a lot better after that too.

What model Magnaflow cats did you go with, the ones they recommend for the type of vehicle on their website? I read on other forums pple r putting different model cats and are hit and miss.
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ccc13
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PostPosted: Thu Jun 12, 2014 12:56 pm
Post subject: Re: Misfire and cat issue...perhaps

I'll check my purchase history... it was like 2010.

Edit: It was 2011, and I love Amazon. Magnaflow 54305, $142.10 for both. Looks like they're a few bucks more expensive now.
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bmw325i
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PostPosted: Thu Jun 12, 2014 3:09 pm
Post subject: Re: Misfire and cat issue...perhaps

ccc13 wrote:
I'll check my purchase history... it was like 2010.

Edit: It was 2011, and I love Amazon. Magnaflow 54305, $142.10 for both. Looks like they're a few bucks more expensive now.


Thanks for the info. Would it be better to drop and take the exhaust to the shop or take the car for better fitment of the new cat. I just want to make sure its weld it properly i guess. Rolling Eyes
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ccc13
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PostPosted: Thu Jun 12, 2014 3:12 pm
Post subject: Re: Misfire and cat issue...perhaps

I just had it done at some random crappy place like Midas or whatever (on the car). They did fine; it's really not that difficult of a welding job.

Also the exhaust is pretty much one effing piece from the headers back, so it would probably be a PITA to transport.
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bmw325i
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PostPosted: Thu Jun 12, 2014 6:49 pm
Post subject: Re: Misfire and cat issue...perhaps

Is it ok to replace just the faulty cat, or I have to do both?

I am reading online the magna 53005 is the same as the 54305 just different finish. Did you get any CEL or other codes pop up after you installed them?
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ccc13
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PostPosted: Thu Jun 12, 2014 7:43 pm
Post subject: Re: Misfire and cat issue...perhaps

Definitely do both of them, and see if your valve cover gaskets are leaking too. I had oil in the spark plug wells (jeesh). Definitely contributed to unburned fuel/oil going through the cats.

If the other model is the same internally, cool. I had a single cat efficiency code pop up like a year later for one drive cycle, and never saw it again. I'd say they're a safe bet overall.
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bmw325i
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PostPosted: Fri Jun 13, 2014 10:37 am
Post subject: Re: Misfire and cat issue...perhaps

I did the rubber mallet test on the bad cat and it sounded like all kinds of things were broken inside of it, another assurance that its bad i guess. I ordered a new cat.



Is it ok to drive the car with the pre-cat sensor off on the bad cat side or i have to unplug both pre-cat sensors until i get it fixed?
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ccc13
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PostPosted: Fri Jun 13, 2014 1:56 pm
Post subject: Re: Misfire and cat issue...perhaps

The best option would be to park it until you can fix it, but if you're going to drive it I would pull both of them out and drive gently. It's loud.
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bmw325i
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PostPosted: Mon Jun 23, 2014 10:11 pm
Post subject: Re: Misfire and cat issue...perhaps

The mysterious misfire on cylinder 7 continuous. I swapped coils, changed spark plugs and still get the P0307 code. What else should i look into, replace the fuel injector?
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