Our mini has started to occasionally sound horrible and occasionally (or nearly) stall on startup. This isn't every time and to the best of my knowledge is when the engine is cold, typically after sitting overnight. This culminated this week when my wife, who uses the car daily for commuting told me that the check engine light appeared. I check the codes and got PO302 and PO304 (I think these are the ones). In either case, two cylinders had misfires. This has only happened once, but the problem is getting worse.

I've read through posts on this forum about the possible causes, and one of the leading possibilities is carbon buildup. We're at 75000 miles, and I don't think its every been cleaned. It seems reasonable that the walnut cleaning may help or fix this problem.

Since my wife depends on the car, and I'm quite busy myself, we'll need to pay to have this checked out and if necessary fixed. I wanted to get this thread started to try and get some help in determining the likely causes of this problem and more importantly to help ensure that the problem gets fixed the first time.

The car will hopefully get in for service this week. I'll make sure to pass on any helpful ideas to the service advisor. I'll post back with any new information.

Thanks.

My 2010 had similar symptoms, rough idling when first started, almost felt like it was going to stall, stumbling, usually in the morning. I had about 25,000 miles and got the intake valves walnut blasted. Symptoms went away, car felt like new. Now at 40,000, symptoms are back. I'm taking it into the dealership tomorrow since it's still under warranty. I'm betting it's carbon, for both cars.

I've been putting off getting an oil catch can, but I really think our cars (07 - 10 DI motors) need them desperately.

Many will say get an oil catch can, but the walnut shell blasting service is inevitable. I wouldn't waste my time on an oil catch can when I already know I'll do the service every 30-40k miles anyways. Doesn't bother me. If any of you are in SoCal I can get it done for a good price too.

I would start with carbon cleaning and also spark plugs if they haven't been done yet.

Be careful suggesting things to SA's. Some get offended. Also, I've had some only look at the one spot if I suggest something instead of a thorough inspection.

Thanks for the comments. Any thoughts on whether I should take this to an indy or the stealer? I figure if I need the walnut cleaning, the indy may not be equipped to do this job.

Some of the independent shops have wised up and bought the stuff to do the carbon cleaning. From what I've heard they're generally about $500 vs $800 for the dealer. We had ours done at around 30k so it was under warranty. Similar symptoms to what you're describing.

The dealer has been unable to get the car to throw any new check engine codes, and according to my wife, they were a bit miffed by the fact that I cleared the codes that caused us to bring it in originally. Oops. So really, no news at the moment.

They still didn't get the car to throw new check engine codes, but apparently its stumbling/stalling on start for them occasionally. For some reason my SA doesn't want to recommend the intake(walnut) cleaning until it throw codes.

On the other hand, we're supposedly 10k overdue to replace all the cooling hoses and they want north of $1k to do it. Apparently they need to drop the subframe to get at some of these hoses, and its a 5 hour job. I didn't expect this and haven't had a chance to look into this 'PM' to find out exactly what they're doing and if its reasonable for us to pay them to do it. Any help?

They want to keep it another day or two to try and get the car to throw codes, but I'm inclined to ask them to do the work regardless. At least it give me some time to decide if I want them to do the cooling hose job or not.

Dealer is trying to rip you off....IMO.
Drop a subframe to change coolant hoses....5 hours?! Lol...
Most OEM hoses made in the last 20 years are generally good for about 10 years or so....

There is no recommended coolant hose replacement. As far as the stumble on start-up, yes it probably will need the walnut shells cleaning done and if they were worth their weight they could just pull the intake off and do a visual inspection. It could also be an issue will the high pressure fuel pump bleeding back to the tank. This would be covered under the warranty extension. If your car has never had plugs then its overdue as they are tied to every 4th oil service, for those and id say get them. Honestly it pisses me off to here"we're supposedly 10k overdue to replace all the cooling hoses and they want north of $1k to do it". Its completely false not too mention the k-frame doesn't come out to do coolant hoses. Ive never seen a manufactures recommendation on coolant hoses. And if that was true then every cpo r56 would get one full set of hoses under warranty. That definitely isn't going to happen. Mini warranty would have a COW if that claim came across their desk lol

Thanks for the feedback.

I just took a look at my Bentley. Its hard to get a feel for exactly how much work is involved in changing out these hoses, in all the various job throughout the cooling system, I didn't see anything about the subframe. They do recommend replacing the hoses every four years.

I'm probably gonna pass on it for the moment. Maybe I'll get a quote from the indy we also go to. I doubt I'll enough time try and do this myself.

Honestly the only coolant hoses I've seen replaced on a r56 in are the lower hose due to curb damage and the hose from coming out of the bottom of the expansion tank due to failed connection. I can tell you for a fact the hoses used on a mini for the coolant system are high quality. Good luck but definitely shop around. I'll check the CPO guidelines in the morning cause I must be missing out of a lot of work. Joking

Another update:

The car finally threw the check engine light for a misfire, so they felt justified in advising the carbon cleaning. So they've done, or are in the process of doing this. I told them I don't want the coolant hoses replaced right now. I need to check this out more first. However they did find that the timing chain needed to be replaced. They suggested that by doing it with the carbon cleaning, I'd save a significant amount on labor costs. Still, with that discount and whatever other discounts my SA promised me, they wanted north of $2000 for that job-- holy S***!@!!@^#%$#%. According to the SA, doing the timing chain alone at full price would cost $3000. After doing a few searches, this appears to be a necessary on the R56 and typically expensive job, so I decided to give them the green light on that. The car should be ready sometime today or tomorrow, and I'll be $3000 lighter with a thoroughly raw ***.

I was thinking in get an oil catch can but with your comment... what is the ''walnut shell blasting service'' for? wich contains and what it does?

Thanks a lot!!!!

Well that thoroughly sucks. The carbon cleaning is $800 or something like that from the dealer. I'm not sure how much the timing chain costs but the parts alone are $4-500 and that's not even dealer prices. The good news is your mini is going to be solid after all this gets done. I would bet you'll be shocked at how much better it is to drive. I know ours was missing/stuttering before we did the carbon cleaning and that was at 30k miles.

You can get the whole timing chain kit for 299. It is a long job (9 hours). I had mine done at a euro shop and it was 1200 for parts and labor.
Carbon cleans for walnut shell blasting run about 600 from what I've read. Of course prices vary by location...