I have 2008 533xi. here is the story: one day i couldn't start the car in cold weather. It was cranking 3 times and stops every time i tried. Checked battery- it was showing 11.5V. I took battery home and charged it. Next day installed battery and started the car- car started rough , was shaking and i got 2 cylinders misfires. Swapped coils and spark plugs- no difference- same cylinders misfires. Checked DME- had fried mosfet on cylinder 3. Bought MSD81 programmed and installed. Started the car- cylinder 3 misfire again. Replaced all spark plugs. Now i have no misfires, but car slow to accelerate and vibrating (much less than was before but still). Now i have code P2c77. At the moment it looks like everything i fix something else comes up. Should i go forward and replace HOS2 and hope it will fix loss of power and vibrating or i'm missing something else?

 

Why would you jump to the conclusion to replace the MSD81?

 

i did voltmeter test on mosfets. One of them was fried.

 

I've never seen anyone replace the whole DME for MOSFETs but that is a way to correct the issue. There's companies that replaces them. It seems like it wasn't your issue since replacing the plugs got rid of the misfire. I would also check the injectors because that very well can be an issue.