Rough Idle when cold

[CCTommy]

I have a 2012 Cooper S and when I go to start it when cold it idles very rough until warmed up. Any ideas what could be causing this to happen?

[Luccia at Pelican Parts]

Is your check engine light on? Have you plugged into your OBDII port and checked for faults? Could be a few things, maybe fueling related. The N18's (2011-2013 Cooper S) don't typically have as many issues with the HPFP as the N14 (2007-2010 Cooper S), but it does happen. Their symptoms are very similar to what you're experiencing, but we want to properly diagnose the issue before throwing parts at it, especially expensive ones.

This is for N14's, but you'll want to test your fuel system: MINI Cooper R56 Fuel Pump Testing (2007-2011) | Pelican Parts DIY Maintenance Article. HPFP test is the last figure in the article.

Let me know what you find out.

[CCTommy]

Thanks for the quick reply. I do not have the check engine light on and there are no codes. Will see if I can get the HPFP test done at my friends shop.

[CCTommy]

OK I have checked the rail fuel pressure and it runs around 730 psi without any fluctuations. I noticed that it was running rough and it sounded like the turbo charger vale opened and it smoothed put. Also, the code it gave was I believe FP300, it said it was misfiring. If I give it a little throttle, the misfire goes away and will idle.

[Luccia at Pelican Parts]

FP300 isn't a MINI code so you'll need to use a diagnostic scanner that can read BMW/MINI faults. You can purchase something inexpensive such as the iCarlyApp. Carly for BMW - The Most Powerful BMW App Solution.

When you accelerate does it feel like you have a lock of power or anything? Once you plug in with that and get a proper code we will have a better idea of what is going on. Next, I suggest you check your plugs/coils. When was the last time you replaced them? Start with the basics. If the vehicle is misfiring on a certain cylinder you can remove the plug from that cylinder and swap it with another cylinder to see if it follows. First, plug in with a proper scanner and see what fault you get.