My 07 MCS has about 47k miles at 34k I started noticing that it wasnt running rright. Took to dealer Mini replaced engine 12k later on new motor same problem. Anyone else have this problem? I've used the techron onlyt shell 93 octane everything dealer said.

 

What was the reason for the first engine replacement?

 

If you only have 12K on new motor I doubt it's carbon buildup.
You say it's not running right but that doesn't tell us anything
specifically.
What is it doing? Stalling, idle rough, hesitation, when was your
air filter changed last (a dirty air cleaner can cause rough running),
are you getting any check engine lights, basically, we need more info to help.

 

The first engine they found scorched pistons. The problem that lead to me taking it in was while driving to work one day got off of highway car started sputtering and missing. Apparently they said enough carbon to shuit down 2 cylinders totally 1 partially. I had vehicle serviced 7000 miles after replacement so I hope they changed the filter then. Also I've noticed that my exhaust tips are blacker than normal. I run a 98 honda preelude in various racing formats with much higher octane fuel n less emmission control and not near that black. I'm thinking clogged exhaust. It seems to me to run rough like an inconsitant sputter.

 

Issue on gen2 motors is fuel cleaners DO NOT CLEAN THE INTAKES ON DI motors....
The fuel is injected to late....so pvc gasses condense, and bake, making carbon...later gen2 cars had a revised pvc system....

 

Like drsimmons said, that sounds like an unusually short time frame to be able to build up enough carbon to cause problems. But since it did, I might look to things like how the MINI is being driven. Lots of short, city-type trips where the motor is not able to fully warm-up? Could try a different brand gas (shouldn't really matter, but who knows).

For the present issue, you probably need to get it back to the dealer and see if it is the same carbon problem and see if they can clean it. After that, you may have to be aggressive in doing something like Seafoam treatments as a preventative. Maybe install a catch can.

 

Another thought is if it's a rough inconsistant sputter it may be the HPFP going out (fuel pump). This is still warranted for 10 yrs/100K.
Does it start hard?

 

No it starts up fine, I'm thinking its residual build up in the exhaust. When they replaced motor it was just the crate all existing peripherals stayed. so I'm gonna drop exhaust n see if theresa any build up in pipes. It's inconsistent on issue. I have it serviced religiously. I'm gonna take it to my buddies race shop n have them take a look. Oh It gets driven hard alot of city driving and my right foot is 50lbs heavier than avg. I drive it like it stolen! However I drive all my vehicles like that, my day after purchase ritual is trip to track or private road my Employer had installed just for topspeed test. So yea my driving style is not conservative by any means, this just may be the start to a fun expensive upgrade.