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E63 / E64 M6 (2006 - 2010)

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Old 05-05-2018, 09:50 AM
14rshanahan 14rshanahan is offline
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Location: NJ
Join Date: Jan 2018
Posts: 11
Mein Auto: 2008 BMW M6
Hello everyone,

I have a white '08 m6 with 43k Miles. One day I was driving for about 20 minutes and then the increased emissions CEL came on. The following day the CEL was gone...a day goes by and it came back. There was no noticeable difference in the driveability or power of the car, so I figured it was a bad o2 sensor and put it off. A week goes by and one morning after 30 seconds while the car was warming up the RPMs dropped, the exhaust note was weird, and this went on for a few seconds until the "Engine Malfunction: Reduced Power" CEL came on along with a 5k redline. I turned the car off and back on, and everything was normal. No CEL and the car drove fine. The Engine Malfumction only occurs on cold starts but not every cold start. And it goes away upon restarting the beast...anybody have a similar expeirnece or any input to what this could be caused by?

I had the car looked at by an Indy shop he pulled the codes and said they were misfire codes on cylinders 2 and 3 (302 and 303) He believes it's something with the fuel injection system but he recommended to bring it to bmw since I may be covered under a recall.

Dealership wants to replace my pre cat o2 sensor on bank 2 for $600 (including parts/labor/tax) as some of the wiring "burned onto the exhaust" and they believe this is causing the Engine malfunction. The dealer neglected to mention anything about misfires on cylinders 2 and 3. My question is can a bad o2 sensor cause misfire codes on specific cylinders? I.t just doesn't make any sense to me, however someone more mechanically inclined may be able to answer the question. My SA specifically said they want to "try this" first and see "how things operate and how the tests go" after they replace I.t. Sounds to me like they're trying to charge me for some bs just to tell me I have to replace another part. I found o2 sensors for the '08 m6 online $80-$160 and $450 in labor seems outrageous.
Can the pre cat o2 sensors cause misfire codes on specific cylinders?
My local Indy shop believes it's a problem with the fuel injectors, however they told me this before BMW spoke to me about the o2 sensor and I have yet to hear back from them.
Any help is appreciated!!

Last edited by 14rshanahan; 05-05-2018 at 09:51 AM. Reason: Shorten it
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Old 05-16-2019, 09:14 AM
bigblueoval bigblueoval is offline
Location: Statesboro Ga
Join Date: Mar 2012
Posts: 50
Mein Auto: 325i
I've had his problem twice on my 07 M6. Once it was the thermostat (800) and once it was the IAC. (1800). Good luck
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