Long story.. My '05 R53 (155k, completely stock at the time) went bonkers a while back. My family and I were out running errands, had been on the go for a few hours, so it wasn't a cold start problem. The first instance, I took off from a light, and it stumbled, hard. Like leaned you forward in the seatbelt hard stumble. I stepped on the clutch and gassed it, assuming I just screwed up my timing and almost stalled it. It took off as normal so I assumed driver error.

Later on, we were just driving down a 4-lane at 40 mph and it did it again. But before I could get my foot on the clutch, the power came back and it was back to normal. The farther we went, it repeated periodically, got more frequent, and worse, even completely stalling sometimes. Once we could, we turned around to head back home, and it just kept doing it over and over, so we stopped.

I have a code scanner, so I went to pull codes and it gave me nothing. The EML light hadn’t even turned on. After a few minutes I decided to try to limp it to my friend's shop. We made it to the interstate with the same symptom repeating at seemingly random RPMs, when taking off, driving at an even speed, or clutch in coasting to a stop light. As long as I was on the highway though, the power loss repeated many times, but after a second or even a few it returned to normal power. I was able to maintain safe highway speeds in the right lane, and It never completely stalled once.

Once I exited though, it was back to power loss, normal, power loss, normal, stall, etc. To add insult to injury, my loving wife pointed out it probably looks to everyone else like I just can’t drive a standard. Ha. Ha. Ha.

Anyway, I managed to get it to my friend’s shop and we got a lift home. We spent a few days trying to figure out where to start. In some of his resources, there was more than one instance of other techs presenting similar symptoms and they concluded even in an absence of a code, it is likely a failing crank sensor. With everything involved in replacing that, I decided to go ahead and do some other stuff "while I'm in there". New thermostat, new water pump, crank sensor, hoses, o-rings, gaskets, 15% pulley, belt, cooler plugs, cooling fan relay needed done, and we did the supercharger service too.

I drove it for a few days after and it was all good. Then I'm sitting in a parking lot, with the car at idle, and it suddenly misses ever so slightly. Then again. Then a little more. Then it smooths out. A few minutes later, a slight miss, vibration, and its gone. Then on the way home, it starts that old power drop to almost a stall again. Ugh! Oh, this time it threw a code, P0172 Mixture Control (bank 1)-system too rich. As it didn't throw that code, or any code before, I am unsure if it is related. I torqued my left ankle a couple of weeks ago, so she has been sitting in the driveway begging me to take her for a drive, but I'll drive her tomorrow morning and report here if anything happens.

Has anyone run into this or anything like it before? I've searched here, I've googled, I've asked in my local MINI group, etc. That last one got me one suggestion, that the crankshaft pulley may be coming apart. We didn't pull it, but I think it would have been obvious if it was coming apart. Am I wrong? Oh, there is one other issue I've been having, may or may not be related. Under hard acceleration, higher RPMs, I get quite a lot of pinging, unless I'm running 93 octane. I live in Oklahoma, about 1200' elevation. It pings with 91. It pings a tiny bit with 91 and octane booster, but no pings with 93.

Any suggestions?

Chris

 

Did you check the vacuum hose from the intake manifold to the fuel pressure regulator? These things come off very easily, I replaced it with some quality vacuum hose with some proper clips. Its a design flaw if you ask me, should be secured properly

 

Pull your spark plugs and take a look at them, you can tell how your engine is running by the plugs. (see link)
https://ngksparkplugs.com/en/resourc...gine%20damage.

155K miles... have you replaced the fuel filter? Serviced or inspected the fuel injectors?

And depending on the service history many of the vacuum line connectors, pipes hoses and the like do perish over time and need to be replaced. e.g., the o-rings sealing your MAP sensors, and the vacuum hose connectors like on the hoses above.

Best of luck.

Motor On!