So I noticed strange startup tach needle movements in my 2012 MCS in my 2nd month of ownership last fall as the temperature dropped. The RPMs would rise as the engine started up an then would immediately drop below 500 RPMs causing the engine to sound like it was going to stall and then RPMs would rise back up. I mentioned it to the dealership when the car stalled at startup on 2 occasions and they told me that I had stalled the car?!? I told them the clutch was to the floor, I wasn't in gear and the car was parked but since there were no codes nothing could be done. I religiously fill the MINI with Shell 91 and check my oil weekly and it hasn't shifted from the center of the dip stick. My fuel economy has also been good with a slight overall improvement over 7 months of ownership.

The car continued to act a bit wonky at startup throughout the winter but did not stall again. This spring, the problem has changed slightly. When the temperature is between 0-10 deg Celsius (32-50 F), the car seems to struggle at startup with the revs bouncing around a bit and then when I start moving, the car lurches violently 3-4 times during any kind of acceleration (even gentle) for the first 50-100 meters and then goes back to normal. The lurching is like that of a first time manual driver trying to shift but occurs while driving in gear (my shifts are still smooth during the lurching period). The lurching occurs following the first startup of the day when it is cold, and usually on subsequent start ups that day the car will not exhibit the strange behaviour.

In the past when I have taken the car to the dealer for cold weather issues, by the time my appointment date shows up, it is too warm and the issue doesn't manifest. I am hoping someone here has a theory as to what this might be or has had a similar problem fixed in their MINI.

 

Disclaimer: I'm far from an expert here, and I'm just thinking out loud.
We have a combination of cold ambient temps, and the ECU running in "open loop" that are causing a driveability issue. In open loop, not all sensors are being utilized, and the ECU is substituting pre-defined values. Such is the case with O2 sensors, that do not function correctly until they are warmed up. So when the other sensors come online, they allow the ECU to compensate for whatever is wrong. Or the issue might simply be a fault with the Open Loop values themselves (I find that highly unlikely).

I almost want to say that I suspect the coolant temp sensor, which I believe is read during open loop operation. I'm not sure about your 2012, but I know my 2002 uses only a single coolant temperature sensor. If there is a fault, there is no point of reference for the ECU to compare against. Yes there is an ambient sensor, but it's very possible for those two temps to vary in normal operation (such as hot start, or if a block heater is in use). My uneducated hypothesis says that if your coolant temp sensor is reporting that the coolant is significantly warmer than it actually is, your engine is running lean during warm-up, which could cause the low RPM you described. ECU senses the engine is about to stall, and sends a bit of extra fuel, which causes the rise, and the cycle repeats itself. Obviously driveability problems will ensue. Codes are not logged because the ECU does not know the temp sensor is faulty, and thinks the RPMs are dropping due to load on the engine. With the O2 sensors offline, ECU does not know the car is actually running lean.

The way to confirm or rule this out is to find out what the value for that sensor should be at the actual coolant temperature, and either backprobe the sensor, or read it using a tool such as BMW DIS. Since the sensor may report correctly at higher temperatures, it would be best for the test to be conducted with coolant at the temperature at which the problem presents itself. This could be done by removing the sensor, and placing it in chilled water. At this point, any shop would probably just replace the sensor with a known good unit, as something needs to plug the hole in the head so the coolant running out will be minimal. Plus the warranty is going to pay out the same tier labor regardless.

Good luck in solving this troubling issue, and please report your findings.

 

Ask about the fuel pump. Just because it sounds similar to what happens when the fuel pump starts crapping out.

 

Thank you both for weighing in on this issue , I will try to ask about the sensors and the pump and try to shoot a few videos before my service appointment. Hopefully this gets sorted and I can post a happy ending soon.

This is a quick clip of how the engine started today in cool (8 deg C, 46 deg F) weather. I am just curious if this is normal for anyone else.

http://www.youtube.com/watch?v=VMR3h7hgTrw

When it is warmer out the rpms rise to 1100-1200 rpm and just stay put. During the winter the cold starts could be much worse than this video and result in the tach needle jumping around multiple times before settling down at 1000-1500 rpm.

 

I have similar problem:

https://www.northamericanmotoring.co...nce-again.html

Delaer never done anything about it.. couldnt replicate problem blah blah blah..

It happens not and then.. I got use to it, till it will break down finally, if so. Otherwise car is running just fine.

 

cub: wow that thread of yours took a wrong turn to nowhere. I also got used to the engine coughing a bit during startup, but the 3-4 lurches it now puts out in the first minute of driving are what worry me and also freakout my passengers. I guess the two issues may not be related.

 

Ok,just to throw another thought on your issue ......the infamoous carbon buildup can cause irratical rpm s The D/I. engines are known to coat the valves with thick blakened tar like residue.The only cure for this problem is to have more frequent oil changes and consistently monitor your oil consumption.Also as I have stated time and time again use a top tier gas 91 octane or better (I have always used shell V Power 93 and have over 65000 on my '07 mcs with virtually no problems.Hope you find an answer that corrects your problem.Just throwing my thoughts out there.

 

Sidthekid,
I have a 2012 as well, and the EXACT same cold start issue, except no lurching. I always let the engine warm up for about 5 to 10 minutes when it's cold outside in the morning(maybe why mine does not lurch)
When I talked to the dealer they told me it was "normal" due to a combination of the temps, variable valve timing/lift, and cold start(open loop). They said the engine takes a second or two to "find idle" and that I have nothing to worry about. Only 1600 miles on mine now, and the problem seems to be getting better. Who knows?
Let me know what happens with your service appointment if you can, I'd love to know what they tell you this time around.
Thanks,
D

 

I gather tha this is becoming a more common issue with this engine.
I too have had the same fault on my 2012 MCS - 12000KM so far. The OP's description is right on the money!
I too have taken the car in and have been advised I have no problem - all is normal.
I have tried different fuels with no difference. Damp weather when the car has been cold soaked down to 0 to 10C seems to be the range, and I think it may be hapening between 35C and 45C coolant temp as per my EcoRout gauges. I need to catch it a few more timed to make that last correlation.
To add to the misery, it doesn't 'show' or sound like anything when videoed on my phone...
When I posted about it a few months ago, one suggestion was to have the coolant temp sensor replaced, and after a bit of searching I did find a couple of folk who did have theirs replaced on spec, and that seemed to sort it for them. I have not been back to BMW to see if they will replace mine on spec, that being said mine has 'only' lurched and burbled since the time I did have it in - it hasn't done a repeat of the full on "start, cough, die, repeat" scenario to me yet...
Good luck and keep us posted!
Eric

 

Around here there is a 1 month lag to see the service dept unless your engine won't start. I asked if the engine lurching was concerning, their response was no codes and could not replicate so I guess I will wait till the fall and then hope it is nothing serious that is damaging the car. As far as the fluctuating revs go I can understand that it is normal but the engine stalling occasionally at cold start is another thing they could not replicate. Some people think I am being too **** about these things, so it is good to see other people are also concerned by them. I will update this thread if the deal ever replicates the issue.