I recently bought a 2011 Clubman Justa (so N16 engine). It has a terrible "misfire when hot" problem. I have read through various posts here and learnt a lot from them, but stil have some questions. My goal now is to understand if I have a valve seat problem (which means it will need a head job) or a valve stem seal issue (or if I am missing something completely)

Here is some history:

1. When I bought it, I unfortunately did not have a very long test drive. There was no check engine light and it ran smoothly. I came home ( 70- mile drive) and I got the check engine light. It also had very bad misfire especially on idle or low speeds. Scanner pointed to bad VANOS solenoids
2. I changed the VANOS solenoids and it did reduce the misfire issue a little, but it was not gone completely. (so it probably had multiple issues)
3. Parts cannon: New Iridium plugs, new coil packs and new MAF sensor (MAF was technically not throwing parts because I did get a MAF plausibility error in the scanner)
4. Observations: Second cylinder always gets misfire (sometimes misfire on multiple cylinders too). Spark plug in second cylinder is aways oily and sooty. And there is surely burning of oil (I read a circular from Mini that says it is normal for minis to burn a quart every 750 miles. I am new to mini but not new to cars, isn't this insane??). Compression is good in all cylinders with very little variation (between 12 to 13 bar)
5. If I remove the camshaft sensor when the engine is misfiring badly at idle, there is a loud hiccup and then it runs smoothly. Based on this post, looks like I have a valve seat problem. This does make sense considering that the VVT is disabled when you remove the camshaft sensor.

https://www.northamericanmotoring.co...hot-fixed.html

6. The symptom related to valve stem seal issue is often burning oil and blue/grey smoke. I am burning oil and the second cylinder is oily but I don't really see blue smoke. The exhaust does smell different (like burning oil).

So, although from the above link it is pointing to a loose valve seat problem, I am hoping that my diagnosis is wrong and I don't need a head job. Is there something I have missed? By watching YouTube videos I have learnt that I can do the valve stem seals repair without removing the head and this is something I can perhaps do myself. Financial situation doesn't allow me to spend thousands of dollars at a shop.

What do you suggest? Is it surely a valve seat issue or valve stem seal changing could potentially solve the issue? Perhaps I should change the valve stems (because there is a procedure without removing the head) and check and then remove the head and take it to a machine shop?

Thanks for all your help in advance!!

AK

 

the safest way to go forward with this is to send a camera through the spark plug hole and confirm your doubts.

I had a mini that would only misfire above 3k rpm. after swapping plugs, coils and injectors, the ecu was the only thing in the way. I replaced it and the problem was solved.

 

THanks. What should I expect to see with the camera?. Since the valves are on the top, how can I see anything unless I am able to turn the camera facing up? I do have a scope and can try that.

In my case, thought, the misfiring is mostly when I slow down, or at idle. misfire is surely more pronounced at lower RPMs.

I would also like go provide some new updates:
1. I used Lucas oil to make the viscosity a bit higher. It did not stop misfiring, but the amount of shaking of the engine on misfiring is surely reduced. I also read elsewhere that you can use such additives as a temporary solution before you get a chance to do the head job. My last oil change was 5W30, but considering the oil consumption after I fix the issue I plan to go with higher viscosity and some people have reported less oil consumption using 0W40.

1. The MAP thermostat activation code has now shown up (2EE5). Misfire was there before this and is still there. I don't think this is related to the original issue but of course will need to be addressed.

 

there are some cameras that can look up at the valves. i would first check the piston head to see any signs of damage. with the seat flopping arounds, i would guess there would be some sort of top end knock!?

another way to check the seats, maybe through the injectors' holes or remove the intake manifold and check from there. also, a leak down test might lead you to where the pressure escapes to.

 

Thanks for your responses and sorry for delay in responding. I was finally able to look at the valves using an articulating endoscope. Valves on cylinder 2 clearly show a huge gap. I forgot to keep track of the orientation so could not tell if they are exhaust valves or intake valves. I also recorded a video, perhaps someone can comment on this? Also took images in one of the good cylinders (#3). I guess the clean ones are intake and dirty ones are exhaust, but all 4 seamed to be in closed position in the good cylinder. Comments are welcome! Cylinder 3 is good and Cylinder 2 is bad. Can you tell if this is a sign of loose seats or bent valves? I have seen some photos of dropped seats in which you can actually see the ring (seat) but I don't see it here.

Regarding damage on the piston, I am not able to tell because it is so much full of oil deposits. Also these pistons have those clearances for valves so I guess they are less likely to get damaged?

Valves Cylinder 3 (good)

Valves Cylinder 3 (good)

Piston Cylinder 3(good)


Piston Cylinder 2(bad)

Valves Cylinder 2 (bad)

Valves Cylinder 2 (bad)

Valves Cylinder 2 (bad)

Valves Cylinder 2 (bad)

Valves Cylinder 2 (bad)

Valves Cylinder 2 (bad)

 

Attaching a video. (avi file)
Thanks