We have a mini cooper 2008 with ~150 K miles. Started misfiring on cylinder 3. Generally runs fine but after warm-up (45 min) and on a long downgrade, I feel the stutter and the check engine light comes on.


After a misspent $3,200 without resolution, the diagnosis was the valve stem sheath randomly allowing oil to be injected into cylinder 3. Any thoughts or other similar experiences? I can predict when its going to happen on a descent grade after warm-up.

 

ALWAYS check for codes. Does it say P0303? what are the codes? what has been done on the car so far? where are you located?

 

Yes P0303 on code reader. spark plugs, hot and cold compression check, oil change, oil additives, fairly complete internal diagnosis. Central CA Santa Cruz Mtns

 

do you remember the compression numbers?

are you burning/loosing oil?

 

Compression numbers in range. Yes to losing oil. 2 or more quarts between changes. Doesn't smoke.

 

if compression in range, that makes me believe the chamber is "healthy." Now, you have to check on your fuel injector. although rare they do bad, i suggest checking it. take the plug out and run the car. see if you can notice gas puffs or gas smell. also, with the carbon build up, the injector might have some buildup on it too.

 

Thank you for the insight. Would a fouled injector present misfiring randomly? At low rpms the car loses power. It also rough idles and misfires when descending a hill after operating smoothly for some duration. Almost like there is a build up of some sort.


The question is why it would operate perfectly for most of the time then not.

 

with 150k miles, the injector may have reached its life expectancy. That is why i'm suggesting to check it to make sure it is/isn't working right.

The shaking is the after math of a misfire.

 

Thanks - we'll check the injector.

 

Hello, all. I need your help.
I have 2010 justa and had misfires (can't remember which cylinders) last Nov. and did seaform few times and it seemed all got cleared. Few weeks ago, the idle rough came back (always happens when the engine is warmed up - 20-30 min) and got P0301 code. I did normal troubleshooting (switching the coil and plugs), but always comes back with P0301. I am about to do compression test, but before that I looked inside the pistons and found something I was afraid to see. Sorry for the blur shots, but the cylinder 1&4 have black buildup or something (more on cylinder 1 than cylinder 4) that I don't see on cylinder 2 &3.
The Mini has been relatively trouble free and has almost 140k miles on it. What course of actions should I take to resolve this issue or do I need to start looking for another car?

Thank you for your time and your help in advance.




Cylinder1



Cylinder2



Cylinder3



Cylinder4