I'm having a bit of trouble with my R56S, the problem has only just cropped up today.

What's going on is:
Idle is rough - every 2-3 seconds there's a drop in RPM from the 800 idle to about 700 and a shake through the whole car.
When stationary, the car will hold RPM above 3k without a problem, but anything below and the "roughness" from idle is more noticeable.
Some surging when under slight throttle.



There isn't a CEL, but I've connected my ODB scanner and used Torque to scan - it's showing a misfire on cylinder 4 (the other 3 are normal) and a test fail for "Fuel System Monitor Bank 1".

The car's got a little over 68k on it, and is an '07.

I've had a google for the symptoms, but the causes seem to vary from the HPFP to carbon build up, to burnt exhaust valves. Is it a reasonable guess that with the fuel system test fail that the HPFP is on the way out?

(The car's booked in with Mini for Tuesday, so I'll know more then, but thought someone more knowledgeable would be able to prepare me before handing it over to the dealership)

 

Start by pulling the plug. All the other things you mentioned can be an issue and can cause your problems. Run some Techron thru it and see if it clears up because maybe a injector is clogged. I hope IMO you have been running 91 octane or better. Do you have a warranty still? I hope so if it turns out to be one of the more major things causing it. Good luck and keep us posted.

 

It's still under warranty, which is why my wallet isn't trembling! 97 RON or better is all it's been fed on. I'll pull the plug HT lead and see if there's any damage to it or it's not seated correctly, but I can't imagine that to be the case.
Plugs were changed at about 45k IIRC.

 

Well if the plug does not help, try moving around the coils and see if the problem follow it. IF it does you have your answer. If the plugs and coil are fine, you could have a bigger problem. I would guess at the HPFP or carbon build up as being the problem. Usually you will get a CEL with any of these issues. Good luck

 

Thanks Braminator, just tried the plugs - no change. Still bad.
Have taken a video to show to the dealer incase it magically decides not to repeat itself when they have it.

Will update when I've got more info!

 

Good luck.

 

One thing I have just noticed is that the usual whine of the fuel system priming when the car gets unlocked, isn't happening at all.

 

Maybe a fuel injector? I don't claim to be a mechanical expert or anything, but my BMW 335i (turbo) has had two problems similar to what you're describing. One time it was the high pressure fuel pump and fuel injector. The second time was a fuel injector. Replaced 4 of my 6 injectors and I think I'm about read to replace the next two...

Good luck and post the results!

 

Thanks for the heads up.
It's in on Tuesday for a few hours for them to have a look, will report back then! It's not much worse since Thursday. I've got a long list of notes to give to MINI about what's been happening. Will be posting the results when I know, hopefully it'll help other people diagnose the problem/s later on!

 

I would be very surprised to hear it was an injector as they rarely fail in MINI's from my experience.

 

As promised, an update: Mini had it for 2 hours today, in that time they verified the misfire, swapped the coil for cylinder 1 with 4 - the misfire stayed on cylinder 4, so it's not the coil packs.
It's back on Thursday for the whole day for them to start taking things apart, tech suggested it could be burnt exhaust valves.

UPDATE: After Mini replaced the spark plugs, all is well.

 

always good to interpret the spark plugs when pulling them out, they are super easy to replace anyway. over time and through detonation the plug gap can widen causing it to be out of range, and cause misfire. if it got to that point of misfire because the plug was worn with a gap too big then it's safe to say that cylinder received quite a bit of knocking before it was worn so bad to miss. FYI spark plug intervals are recommended every 60k miles. I do them before then though since they're so easy to replace and not super expensive.

 

GOOD LORD!! If MR CHOW just needed new plugs, I'd be the happiest motorist alive!! Unfortunately, new plugs were just installed within the last thousand miles, so I'm doubtful it's that simple. :(

 

Ouch! I hope Mr Chow is better soon.
Strange thing is that these plugs were new 18k ago... bizarre! Here's to hoping nothing else goes wonky after the warranty runs out next month

 

As it turns out, MR CHOW has a cracked piston and needs a new engine at 55K miles. My MINI dealership is trying to get some help from MINI USA.