2008 Cooper S with 88,000 miles - I've seen others have had stumbling issues while accelerating, but no stalling. I had the stumbling issue today, and it actually stalled. I was accelerating and felt the stumbling for a few gear changes and then the rpms dropped to 0. I pulled over and tried to re-start. It would start, the rpms would jump up and down a bit then stall. I finally got it started again and drove very slowly home.
I just got it back from a service, the items that were done:
- Brake fluid change
- Oil change
- Fuel induction service
- Valve cover assembly replaced
- Water pump replaced
- Vacuum pump replaced
Fuel induction service would be my first suspect as the issue, but I don't smell gas, so I don't think I have a leak in the fuel line. What else could be the problem? Spark plugs? Coils? Thinking about it now, I'm the second owner and have put around 30,000 miles on it, and I don't think the spark plugs have been changed during the time I've owned it (I think most other cars have 15,000 mile interval for spark plugs?).

 

The stumbling came after service of the car?

 

Yes, this all happened after servicing, same day in fact.

 

Obviously you need to go back. They probably left you with a vac leak somewhere with what they did.

 

It definitely sounds like a vacuum leak most likely a loose vacuum hose clamp, I've seen this happen to countless others after simple repairs. You likely have codes stored so I would take it back to where you had the service. This is why I like to perform my own maintenance. I don't trust anyone to change my oil, bad experience once.

 

It's going back in on Monday. Given that the vacuum pump was replaced, I suppose there could be a leak if they didn't put it all back together correctly (would not be surprised if they were in a hurry and missed something). I used to do all my own maintenance, the Mini is probably the first car where I've had everything done by the dealer or a local shop. Must be getting lazy in my old age. Next car, I'll probably try and get back into wrenching on it myself.

 

Sounds like symptoms of a bad HPFP or buildup on the intake valves, but curious it started when you had all this work done to it.

 

Was the CEL on? As Steve pointed out, have you done a carbon clean up yet? Not that this is your issue, but would be curious as to what the build up on your valves looks like. Info about the clean up at post #6 here. Anytime work is done at a shop and your vehicle exhibits issues that were not there previously, it's always good to bring it back right away. Be sure to report back and let us know what they find out!

 

No CEL, and no codes were stored. I've not done a carbon clean in the four years I've owned the vehicle, and I'm guessing the previous owner probably didn't either. Hopefully, they will figure out the issue tomorrow.

 

Diagnosis - HPFP.

Should be back on the road tomorrow.