So a week ago I started getting a missfire and backfire from my 2010 mini s. I had the valves blasted at 65k and it's currently a hair under 90k. I've also been doing seafood treatments every 1000 miles or so, with more frequent oil changes than suggested by mini. Upon startup it seem to idle smoothly, but after a cold start any mid-to high load to the engine or revving will cause the engine to missfire. I pulled a cyl 3 misfire code, nothing else. Spark plugs have been changed within the last 500 miles, and have regularly ran techron through the fuel tank. I can't remember which cyl position is the third cyl, but I do remember that I found two spark plugs loose after I had my valve cover replaced at motorworks mini in Golden Valley, MN. Crap dealer "long story". The coil on one of those two cyl is stained brown at the bottom but still seems intact. What are a list of things besides moving the coils around from cyl to cyl that I should be checking. I was pointed in the direction of the hpfp by checking fuel rail pressure, but don't know the stock specs, and when I checked through torque it seemed pretty steady, and would climb under acceleration. I'm used to working on bmw's i6 engines and fuel systems, but this is a bit alien "minus the basics". Any info or help would be great. ~thanks

 

Mine was doing the same thing today after I pulled the cam cover off to make sure the chain guide was ok. I put the cam cover back on and drove 15 minutes to the store, and it ran perfect. When I started it back up, it was running on 3 cylinders all the way home. The tab on top of the #2 coil wasn't staying clicked down all the way, causing the wires to disconnect. The tab only had to be raised a few millimeters and the cylinder would shut off.

 

Seafoam doesn't help. The Gen2 has direct injection so the seafoam does not get into the ports and clean the tops of the valves. It's either the walnut, sea shell or cleaning by hand that works. I use Techron in fuel as well, but none of the additives get to any of the ports or the valves. If your MINI has the noise maker get rid of it. I just did and the next time I want to clean the intakes it will be much faster.