Hey guys about 6 months ago I bought a used 2012 Cooper S. The car's been working perfectly until a few days ago. I was on my way home and 5 minutes after leaving the office. I noticed a major power loss and the CEL came on.

My code reader is saying that there is a misfire on cylinder 3. I've replaced all of the spark plugs with a .44 gap (recommended by the parts store). Cleared the code and took it for a test drive. Still hesitates like it's going to die and I basically have to floor it to get it to move. Didnt see any damage to the coils, but I am planning to switch out 2 and 3 to see if the problem moves to another cylinder.

This is my first DI engine, but I've read some horror stories about carbon build up. A BMW guy recommended trying seafoam, but I do not see that as a viable solution, more like a band-aid to a bigger problem.

I'm running out of ideas and my last option is to take to the shop, but figured I would try a few things on my own first.

I do enjoy driving this car and it's go-cart like handling. I've thought about purchasing another one just because they're so much fun to drive. Although after barely working on this engine, the concept doesn't seem to make a lot of sense and I'm wondering if BMW got it wrong. The owner of my company just recently took delivery on a 740i Xdrive and he's already having problems out the gate. lol

I would appreciate any help! Thanks.

 

Do you have any warranty left? If under 50k miles, you should check..

 

It sounds like you purchased Denso 3461's and gapped at .044", right? Did you torque them between 14.5 to 17 lbs/ft?

I would have purchased the NGK (5992) ILZKBR7A-8G which is gapped at .8 mm or .032". Out of the box the gap should work fine but check it anyhow. Terry @ BMS recommends .022" if you are tuned.

I would replace the #3 coil pack.
http://www.ecstuning.com/Mini-2012-C...8B16A/ES28087/

 

+1 on checking that coil, pop it out and look for arching marks on the boot ( cracked ) of it the coil just failed. Factory gap I believe is .8mm stock for those.

 

Az, I do have an extended warranty that I purchased for 2k when I bought the car, but it doesn't cover normal maintenance (except for oil changes). So figured I'd give it a shot myself before going that route.

Device, you're right on the money, they're Denso iridium and they were pre-gapped at .44. I ended up calling a Mini dealer and they gave me the right .32 setting. I'm getting a lot faster at pulling these out! I do not have a tune, but would be interested in giving it a whirl!

ECStuning, you're on the mark as well! I switched two of them around and noticed on the code reader that the misfires moved as well. Bought a new one at O'Reilly (surprised they had it, had a hard time finding the plugs and air filter as well). After driving this car for a few months, I can usually tell when something is off and a second after I started it. BAM! Felt better than ever! All the codes are gone and it feels like it's breathing better than ever.

First time working on a DI engine, so I barely know what I'm doing, but definitely appreciate your replies! The engine seems easy to work on once you get the hang of it but I probably need to grab a manual. Definitely relieved to have it back up and running!

BTW, I'm going take your recommendations on the NGK's. I was in a spot at the moment, but going to pick up some new ones at the begining of the month. And I also plan to replace the other 3 coil packs, you know, just encase lol

Thanks everyone!