2011 Cooper S. I've searched the archives but can't find any matches for this particular problem...

In my case, the car starts fine but after about 10 seconds I can hear what sounds like a vacuum leak coming from the top-left side of the valve cover, at or near what appears to be an non-removable round cap on the valve cover. The engine idles rough as long as the sound of air is noticeable, but the sound stops after about 2 minutes and the engine immediately idles fine from that point on. It drives great once it's warm. I have to think that there is a valve within the cover that is closing as soon as the pressure is correct, but the rough idle is driving me crazy... Ideas?

Thanks

 

Your PCV is going bad. The sucking sound is a leak in its diaphragm. Replace your valve cover.

 

Yes. I had the same thing about 2 years ago and MINI replaced it under warranty on my 2010 MCS. No problem since.

 

As stated, your PCV has failed. If you're 100% that the valve cover is the culprit it's a quick fix but the part is about $350. I've had a couple of leaking PCV vent tubes imitate the same problem as well, and it's a much cheaper fix.

Which ever it turns out to be we have both items in stock and ready to ship.

 

Did the new valve cover solved your cold rough/lumpy idle? Thanks.