[Twoforty]

Codes
* 29D2 misfire cylinder 6,
* 2A43 valvetronic thermal overload protection warning.

Car is 2011 325i N52B25 with only 41000 km since new.
On original coils but plugs were replaced at 15000km during free dealer service, not due to any fault.
After driving over 200km round trip a few days ago, the engine developed severe misfire upon hard acceleration, registering the engine emissions warning light on the dash. The misfire and warning light continued for whole 100km return trip, irrespective of revs or engine load, even idling roughly at traffic lights. "Limp mode".
So the next two days the car has driven perfectly around town as though nothing has happened with no engine warning light again.
Codes were read by a friend, nothing repaired so far.
I'm reluctant to try to drive any long distance again until I figure out what the codes mean and what to fix so it doesn't run poorly on next trip.
So what's the valvetronic warning about?
Why register engine faulty one day then run fine the next?
I'm considering changing a new coil on cylinder 6 ...
What you folks reckon?
Thanks in advance.

[Twoforty]

So it seems that if the engine is redlined then it immediately misfires and the engine emissions warning light comes on. The limp mode misfire and warning light remain until the engine is turned off then restarted. Then it runs perfectly fine again until next redline when the problem reappears.

[8303otte]

If it helps, I had a horrific rough idle on mine, I changed the coils and cleaned the Vanos and it is like a new car. Give that a go, especially as it is overheating, there is also a check valve that can get clogged.

[E92William]

That valvetronic code is usually the eccentric shaft sensor taking a crap which could definitely cause WOT problems. Some other thread a while ago I read some guy talking about that code being a software problem and that the car needed to be updated but I doubt it's that. Change the sensor, need to remove the valve cover.

It could be the motor itself though who knows, if you could swap a known good cheap used one in to check it would be a lot easier than the sensor job.

Swap coils from cyl 6 to 5 and see how it does with the misfire thing if not do the spark plugs too.

[Twoforty]

Hi William thanks for the insight.
You might be onto it with the valvetronic being the problem.
If it was the coil or plug failure you wouldn't think restarting the engine could solve the misfire. Perhaps it's a computer coding fault as you mentioned? That could explain why the limp mode resolves when the engine is restarted.
I've got a new coil on the way to try out. We'll see...

[Twoforty]

Update.
Changed new coil and spark plug in cylinder 6.
So far, no more misfiring or limp mode.
🙂