This has happened three times in our first 800km (500 miles) since rebuilding the head. I swapped the cyl 1 & 2 coils after the second time but it hasn't followed the coil. Spark plugs were new in January.

It can be a bit lumpy idling when warm (it feels like too low rpm).

New battery, water pump, thermostat, eccentric shaft sensor, vanos solenoids, oxygen sensors, timing chain + guides.

It's a 2008 R56 Cooper N12 justa.

Wondering if anyone who knows what they are looking at can see a pointer in this freeze frame data:

 

Engine RPM is too high. it should be less than 1k at idle. Is this because of the issue? did you do a compression test just to make sure? when you clear the codes, do these same ones return?

 

This was while driving at 40km/h.

Didn't do any investigating tonight. Had planned to do a post rebuild oil + filter change before i disappear for two weeks away for work (my wife drives the car). We've tried to keep it under 3000rpm since getting back on the road. The oil looked OK with no particles in it (phew).

I can do a hot engine compression test after work tomorrow.

The rebuild problem was zero compression on cyl 4 - turned out to be four collapsed valve lifters.

 

Collapsed valve lifters? Any pictures? How many miles?

Suggest you swap the fuel injectors to see if the problem follows the injector.

 

130,000 km (c. 80,000 miles).

The engine shop found the four valve lifters with no oil in them. All lifters and valve stem oil seals were replaced.

Will put injector swap on the list of things to try, along with spark plug swap.

 

Ok, we need to get our part names squared away to ensure we're talking about the same thing. There aren't any "valve lifters" in the N12 cylinder head like there are in an over-head valve push-rod engine.

In the first picture below of the intake camshaft, item 8 is called a "roller drag lever" In the second picture of the eccentric shaft, item 10 is the "intermediate lever". On the intake side, the intermediate lever controls valve lift via the position of the DME controlled eccentric shaft. In the 3d picture, you see how the two pieces work together. With that out of the way, what actually collapsed?

The exhaust side doesn't have an eccentric shaft, so the roller drag levers are actuated directly by the exhaust camshaft lobe.

 

Here's a better picture with the VANOS spring and spring compressor removed.

 

Item 9 in first diagram

https://www.rockauto.com/?carcode=1441102&parttype=5548

 

Yea, those aren't lifters. Those are called alignment elements. Oil flows through them, and the roller drag lever pivots on them; you won't see oil flowing unless the engine is running. They can't collapse.

Any chance you have pictures of the problem before it was repaired?

 

No pics.

Those parts are called valve lifters in the rockauto link, and were called that by the engine shop. The ones from cyl 4 were much easier to compress than the others, and than the replacement ones.

 

Interesting, I didn't even notice those compressed when I disassembled my cylinder head; I thought they were solid. It appears not.

Did you pull your cylinder head? You said in your first post the head was rebuilt. Did you change your valve seats?

 

I pulled it and took to the shop. They completely stripped and cleaned it. Valves and seats were ok. I also pulled piston 4 out - rings were good.

 

The reason I was asking was, the valve seats like to fall out of these heads. After one of mine dropped (500 miles after fixing the warped head), I replaced all of them.

http://www.engineprofessional.com/TB/TB113017-1.pdf

 

... crosses fingers.