Hello. I have a 2008 Mini Cooper base with the N12 engine. The car runs very well; however, on the very first start of the day (after sitting 12 or more hours) the car starts but idles rough (RMP fluctuating 800-1100) for 10-15 seconds and then idles perfectly for the rest of the day. There are no codes or other symptoms.

I have recently replaced fuel filter in the tank, MAF, Spark plugs, engine oil, camshaft sensors, transmission oil.

Any ideas?

Thank you,
Ed

 

I'm not sure if this is your problem but ill throw this out there, I had a similar problem in my 2008 cooper. Turned out my thermostat was stuck open.

 

Thanks Royce. How were you able to diagnose the thermostat staying open? My car only idles rough for about 10 seconds and then it is smooth until the next day........so.......I only get one chance a day to diagnose it.
Thanks for your time

 

Took the thermostat off and then saw that it was open by pouring water through it. It was a series of events because it first wouldn't open so the car kept over heating, tested by pouring hot water on it to see if it would open.

 

Dont quote me on this but....it could be as simple as it needing a new battery....

 

Do you notice any hesitation when driving the car?

My 2012 MCS has always hesitated a bit for the first 100M or so of driving on cool mornings after a full cool down (it is more prevelant on damp mornings). I too get no codes and MINI insists there is nothing wrong... When I finnaly did get a CEL, it resulted in an injector replacement.

That said, the car still hesitates, and I suspect my problem may be different as I haven't really noted any idle roughness - or any I have, I have decided is normal as I haven't seen different - 50,000KM or so...

Good luck.
E

 

I'm interested in hearing what the solution might be to this as well. I've noticed my 2007 MC does the same thing...first start of the morning sounds pretty rough and the idle is nasty for about 5 seconds or so, then settles out and sounds fine the whole rest of the day.

Only had this car for about 3 weeks, so.... 57k on the odo. 5MT

 

I still haven't come up with anything. The battery is new (2 months old.) No other hesitation, codes, or issues. Keep the ideas coming please.


Ed

 

Mine does this if I start with AC on.... I'm assuming it's too much for the cold engine.

 

Skakid, Thanks for that info. I went out this morning to try that. I turned the AC off and then started the engine. The engine started right up and ran pretty smooth.


Is this something that all R56 N12 engines do? Or...... is there something that could be causing this?


I appreciate your post Skakid. Thank you

 

It's frustrating because I'm in Texas so it's blazing hot, when I had a truck the AC would start full blast no problem.

 

This sounds like a bad high pressure fuel pump. BMW/Peugeot were making these with a defective HPFP. There is an open recall for the Cooper S's from this period, not sure on the Justa's. Give MINI a call on that.

 

Base '08 MINI doesn't have the HPFP.

My '08 Justa has done the "irregular idle for 5 - 10 seconds" thing intermittently for a long time. Only does it sometimes, other times it starts & idles just fine. No other symptoms, so I just ignore it. Still runs and drives much like it did when new, with around 68K miles (110K KM).

 

Any solution to thia problem???my car ia doing the same running rough for 10 seconds for the first start of the day

 

any solution to this problem?

 

Could be a weakening fuel pump (not the cam-driven HPFP, your N12 doesn't have it). But back in the days when my wife had the N12 base cooper, I had similar symptoms. I replaced the fuel pump and took the injectors out to clean them and pressurized them with carb cleaner and pulsated each one of them until the spray pattern get normalized. After those fixes, cold start rough idle disappeared. That was our experience with the issue, could be different than yours.

 

New fuel pump and injectors.one mechanic said to me that is the valve seats.but i dont believe it if was the vakve seats i would get check emgine light or even i will feel misfire when is hot.the problem is only for 10secinds in the morning and not always

 

 

If you get rough idling on a cold start, do you also get a rattling noise? If so, timing chain.

PS I shall ellaborate - if you get rattling and it is your timing chain, your timing will be retarded due to the excess length of the chain, this can be only a few millimeters but enough = rough idle and loss of top end power, for example, going up a slight hill your acceleration may be down or non existant. Mini do not proscribe any time line/mileage for chain replacement, on average this can be from 50K miles to 100K miles depending upon how it has been driven. Look out for that rattle and change out the chain/guides/lower sprocket and tensioner.

 

 

 

I could believe that it could be the valve seats leaking down overnight. Then you start it and the extra fuel that leaked overnight burns off
Possible leaking head gasket? Had this on my 2000 528I.

 

 

 

Anyone any ideas..

random rough idle usually cold mornings but not always, when the clutch is engaged the revs are all over the place, and placing accelerator on even a small amount makes the revs almost uncontrollable between 200-2000rpm and it stalls.