So we just picked up a used 2010 Cooper S convertible with the JCW added tuning and aero kits.
I realized that when I stop and sit at lights etc, it seems like the car is idling at about 500 and it kinds of sputters like putt-putt. When we have the sport button is use it idles up to around 750 and and the putt-putt stops. Is this normal?
Thanks

 

Could be related to tuning setup in engine from previous owner.
Not that I am an expert...

It is not normal for regular Cooper and Cooper S MINIs. I doubt that JCW from factory do that as well. Is it freakishly cold where u are? Does this happen when the engine is warm and you start the MINI?

Wondering if you have other engine upgrades?

 

That doesn't seem normal. If you are near the dealer stop by and let them check it.

 

Just thinking out loud could it be the guy didn't use Premium gasoline?

 

Not too likely as the computer would compensate for the lesser octane.