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Discussion Starter #1
Hello. I'm the proud owner of a '08 750LI as of the last 7 months. Gradually over the last four months, I've been getting a misfire. It's in cylinder #1. at first I could hardly notice it. Then it would feel like a little shudder during acceleration. Then it got worse and would intermittently misfire causing the MIL light to flash and then stay on. NOW, with every acceleration but especially between 1200 to 2200 rpm it shudders then misfire causing the MIL to light up. I have been driving with my scanner in my lap. When I accelerate and the code comes, I just clear it and the engine runs smooth until the next acceleration.

So far I've swapped spark plugs, coils, injectors and checked fuel pressure.
I also did a compression test( all 8 cylinders were between 150 and 165.
The only codes I keep getting are "random misfire" and "cylinder 1 misfire"

This might not be related but when I fuel the vehicle, the pump keeps stopping as if the tank is full.

My short term fuel trim shows that bank 1-4 is 3.0 compared to 5-8 being 1.0.

I also pulled the both vanos valves and cleaned them for bank 1-4.

PLEASE!! if youhave had this experience and know the fix, HELP ME.
 

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Hello. I'm the proud owner of a '08 750LI as of the last 7 months. Gradually over the last four months, I've been getting a misfire. It's in cylinder #1. at first I could hardly notice it. Then it would feel like a little shudder during acceleration. Then it got worse and would intermittently misfire causing the MIL light to flash and then stay on. NOW, with every acceleration but especially between 1200 to 2200 rpm it shudders then misfire causing the MIL to light up. I have been driving with my scanner in my lap. When I accelerate and the code comes, I just clear it and the engine runs smooth until the next acceleration.

So far I've swapped spark plugs, coils, injectors and checked fuel pressure.
I also did a compression test( all 8 cylinders were between 150 and 165.
The only codes I keep getting are "random misfire" and "cylinder 1 misfire"

This might not be related but when I fuel the vehicle, the pump keeps stopping as if the tank is full.

My short term fuel trim shows that bank 1-4 is 3.0 compared to 5-8 being 1.0.

I also pulled the both vanos valves and cleaned them for bank 1-4.

PLEASE!! if youhave had this experience and know the fix, HELP ME.
I haven't had this issue on my car but have you tried swapping the wire on #1 with another to see of the issue travels with the wire? I am not looking at my car right now so I don't know if it's even possible but I did have similar symptoms when a spark wire went bad on my Porsche.

Sent from my LM-Q710(FGN) using Bimmerfest mobile app
 

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Discussion Starter #3
I haven't had this issue on my car but have you tried swapping the wire on #1 with another to see of the issue travels with the wire? I am not looking at my car right now so I don't know if it's even possible but I did have similar symptoms when a spark wire went bad on my Porsche.

Sent from my LM-Q710(FGN) using Bimmerfest mobile app


Yes, I’ve switched the ignition coils. It’s a coil over spark plug setup.



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Yes, I’ve switched the ignition coils. It’s a coil over spark plug setup.



Sent from my iPad using Bimmerfest mobile app
I am referring to the wiring harness, not the coil. I just looked at an image of one and it won't be as easy as swapping wires between coils because you would have to open the entire length of the wiring harness to experiment with the individual ignition wires.

That being stated, my next step would be to test the #1 coil wire for continuity OR replace the wiring harness.

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Discussion Starter #5
Ok. That sounds reasonable. I’ll try that. Even if I have to make a jumper cable / harness extender. I have several part cars at my disposal. I will post the results tomorrow. Thanks!
 

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Discussion Starter #6
Fcamancho

Wait! Won’t that affect timing? Instead I’ll try to get some actual ignition coil voltage supply readings from different cylinders. I’ll let you know what I find.
 

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Discussion Starter #7
OK. So I've checked the current flow to the injectors and coils. All is fine. I've pulled the VVT module and the DME module. No water leak issues like some experience. I also checked the resistance of the wires from the DME to the injectors and the coils. we are all good there. I noticed something though. When I clear the codes the engine seems to breath better, if that makes any sense. Only when I accelerate again do I have any stumbling. Stumbling stays until I clear the code again. There might be a problem in my VVT module or the VVt motor on the right bank(cylinders 1-4) of my engine. I'll do some power checks and update when I'm done.

Meanwhile, I'm still open for suggestions.
Thanks
 

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Discussion Starter #8
Elusive misfire of E66 solved.

So I found the problem. It’s the Eccentric Shaft. I’ll replace it and post a follow up message, explaining the mechanical functions of this part. Thanks for all your help and I hope this helps someone else and saves them a ton of search and diagnostics time.
 
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