I have a 2010 Mini Cooper S automatic; just turned 83k miles. Have had it for a year now. Once in a while (few times a week) as I go to accelerate I will get like a pre-ignition knock/ping a quick bog and a puff of smoke from the tailpipe. After that it runs fine again. Anyone have any idea what this might be? I just put new spark plugs in it and a new set of ignition coils, but it is still doing it.

 

Could be built up carbon breaking off and getting into the combustion chamber.

 

what kind of fuel are you running? What octane and who's your regular source?

When you "accelerate" is it "floored ..... full throttle"?

What's the condition of the air filter?

 

Originally I was using Mobil 91 octane but about 6 weeks ago I switched to Shell 93 Octane, just waiting on my new K&N filter to come in, and not floored but accelerating like you were passing someone in traffic on the highway.

 

was any work done on the engine in terms of de-carbonizing, chain? how often do you replace your oil?


i think this picture speaks volume....a head i cleaned to put on my car.