The owner of the N53 series engine approached me. The problem – properly maintained engine (all systems working, the engine uses Stratified charge) suddenly started to “faint” on the highway. EML (Check engine) symbol lighted up in KOMBI, and one or even two cylinders were switched off.
The vehicle’s owner stopped on the roadside and restarted the engine as quickly as possible. Surprisingly, the engine restored normal performance! Even EML disappeared!
After a short moment, when checking the error message list in the DME memory, the owner saw the next catastrophe:

All cylinders of the second banks are switched off (obviously, the switching-off happened sequentially). A range of Lambda probe error messages is stored.
But I was interested in another error message; I marked it in the image:

Here, we can see that a short moment before the crash, the injector of the 6th cylinder started to leak strongly. DME has tried to even out the mechanical efficiency in idle, but even reducing the planned amount of fuel injected by the injectors for 3mg/stk, but didn’t succeed. The leaking really has been thorough. It is logical – if any injector starts/continues to leak strongly on the go, the problems can be severe. It looks like the events unfolded as follows:
a. injector of the 6th cylinder (as the error message indicates) started to leak strongly;
b. DME has switched from Stratified charge to Homogenous mode (it’s the action sequence of DME in problematic cases);
c. the fuel mixture in cylinders No.4 and No.5 became lean, misfires started in them, and/or the spar plug of cylinder No.6 was “flooded”; misfires also began in this cylinder;
d. when DME detects misfires in cylinders of the second bank, it switches them off (after a moment, it tries to restore their performance);
e. due to a leaking injector, Lambda probes of the second bank report wholly inadequate values; DME reports it by recording the error messages;
f. the leaking of the injector has been strong, the drop of the Rail pressure is also possible, incorrect fuel mixture in the first bank, as a result – error messages regarding signals of the probes of this bank.
The scenario that some debris was in the fuel is not excluded. In any case – there is a problem with the fuel mixture/injectors.
For some time, the car behaved normally, but after the one-week second crash happened. This time the owner of the vehicle decided to bring it to the BMW dealer to solve the problems.
What do you think the dealer decided to do?
Conclusion – the valve seals should be replaced. Costs: EUR 3700.
The spark plugs of cylinders No.1 and No.5 have been oily.
My only question – does BMW really, in their dealerships, recruit people without any education and experience? And there really is nobody (some experienced colleague) who could help such know-nothing? Is EUR 3700 really such a small sum that could be easily wasted?
The dear dealership, if you are reading this, please, explain:
a. if cylinder No.1 was working (it has not been switched off even once), how could its spark plug have been oily? I will explain – the oil leaked on the spark plug when it was screwed out. Why? Because the valve cover gasket is leaking. Exactly so simple. The same problem applies to the spark plug of the 5th cylinder;
b. if we assume that the oil was draining (without exaggeration) on the spark plug along the valves, I will upset you – replacing the valve seals will not help. Then there should be a HUGE free movement of the valve guide! The head of the engine should be repaired! I can not imagine how colossal damage it should be for so much oil, which can “drown” the spark plug, to leak along the valves;
c. how would you explain that with such a defect of the valve seals, the engine works perfectly, then suddenly “breaks” for 10 seconds, then – again works perfectly? Will you really try to claim that such mechanical defects are sporadic?
d. aren’t you confused with the error messages regarding injectors, switched-off cylinders, and Lambda probe indications? And – precisely, the 2nd bank? Everything is fine with cylinders 1 .. 3; they have no misfires detected, but suddenly the valve seals broke exactly for cylinders No.4 .. 6 and damaged the injector and the Lambda probes (which thou restored after a short moment).
I think that for every technical person, it is clear – the version regarding the problem of the valve seals is entirely inadequate. But – how could this happen to the BMW dealership? How?