Wide open throttle, pedal to the metal, flat out... whatever you want to call it, every time I do it, my 2011 MCS with 47k miles stumbles.

This is the second time it happened. The first time, it popped a cylinder misfire code (P0302). I erased the code, swapped the coils to a different order. The stumbling went away and the code didn't come back... Until recently.

I was flooring it on a long stretch open road when I felt the MINI stumble. A half yellow CEL came on. This time the code was P0303. I did the same thing I did before. This time, the code didn't come back, but the stumble persists.

I can still drive it fast without stumbling. It only stumbles when I floor it. Any ideas?

 

have you had the intake valves walnut blasted ever? See my posts with the troubles I have had.

 

I pushed the Mini again and of course it stumbled, and a code popped. This time it's P0304.

I'm quite certain it's the coil now. What do you folks think?

 

Definitely sounds like a failing coil, how much time passed between the very first stumble on WOT and now? I've also heard of some member's having the very same issue on only WOT using Denso plugs. I would have a look at your plugs as well. If your MCS has the infamous N14 it might be time for a walnut blasting of your intake valves, disregard if you have an N18 engine.

 

Fortunately, I have an N18. Also, I change oil every 7500 miles and use Seafoam at the same interval. It can't be carbon build up. Not yet anyway.

I first posted about this issue last April, so about 8 months have passed. But that's irrelevant given that I only notice it during WOT and I don't do that often enough to know precisely when the coil started going bad.

The question now is, do I go with OEM or performance coils?

 

Did you ever try a new set of plugs?

 

I will change plugs at 60k. Right now, the evidence suggest that the coil is the likely culprit.

I'm thinking of getting IP coils.

 

There's little reason to go IP coils unless you're running say a Manic 2+ Tune and even then you really wouldn't need it. They provide a little more juice but the OEM coils already put out quite a bit already. Thats a long time for a coil to develop a problem and go for that long without any symptoms, if it were a bad coil you would be having issues all over the RPM range especially after all that time.

A bad coil equals misfiring pretty much everywhere, you have another issue. I'm not a fan of those plugs used in the N18, have you even looked at them? Spark plugs tell a story of how you engine is running and not all plugs last as long as they should especially those N18 plugs. This wouldn't be the first time I heard of fouled spark plug causing problems on WOT with either engine.

 

Just had this on my R58 "S". Dealer replaced all four coil packs and plugs, solved the problem.

 

Did you get any codes and just on WOT? Usually when a coil goes bad these ECU's are pretty good a detecting a faulty coil, but if the plugs are bad or fouled they seem to not trigger any codes when the part that's faulty doesn't have an electrical connector attached.

 

I did check for codes and there were none, the check engine light never flickered. It stumbled one or two time weeks apart and then one day bam it would do it about 3,000 rpm's almost all the time. It wa still under factory warranty so I took it to the dealer and they were very professional about it and had it fixed in no time, with no charge. They replaced all four to make sure the others wouldn't fail too.

 

If plugs are the culprit, then how come the misfire code followed the coil that I swapped around?

 

If it had followed the cylinder right after swaping the coil from cylinder 2 into cylinder 3 right in the same day or week, then that would have been the smoking gun, but it took 8 months to get it to act up again because you didn't push WOT. Now if you had gone WOT after swaping the coil you would have more concrete info especially if the code showed up as the P0303, since you waited the better part or a year your conclusion that it's a bad coil is less certain which is why you created this thread in the first place otherwise you would have already replaced the coil.

It could have been a pure random coincidence that 8 months later you get a code indicating that your stumble moved from #2 to #3, if you believe it's the coil that was originally in cylinder 2 that's now in cylinder 3, buy a new coil and install it into cylinder 3 and if the problem persists you know it's something else. I have seen countless members decide to upgrade coils packs because they think there bad and spend all that money on the upgrade only to find out there's that same stumble a little while later, moneys spent problem remains.

I'm going assume you haven't even looked at your spark plugs to determine if there might be an issue since you stated you're not ready to replace them just yet. Swap the coil you suspect and go WOT and see if it follows the cylinder, then you'll have more info to act on.

 

+ coil swap. Also pull the coils , looks for rust and if the boot is cracked or arc marks. Buy One new coil , then swamp one at a time till the stumbles goes away.

 

TL;DR

Replaced coil #4 with a brand new one. No stumbling at WOT.

 

So you were having the stumble and it disappeared right away? If so the coil could have been fine at low loads but couldn't quite handle high current loads, most of the time when these coils go bad they go bad quickly at any load. Yours seem to fall outside the norm, hope it lasts.

 

That what I was thinking.

With the new coil (OEM), my Mini feels and sounds like new again. I go WOT more often than before, because the engine revs so smoothly now. As I've said in my earlier post, I think the coil has been going bad for a while, because I can't remember the last time my Mini hummed like this.