Engine: N53B30

For the exact cylinder: new OEM injector installed (release 11); encoded.
The engine re-adapted.

All diagnostics data: correct.
Replacement of the spark plugs was performed. During it, the service specialist detected that the ignition coil also is quite old, and it too was replaced.

After this service procedure, misfires sometimes could be felt. ELM 327 indicated – the culprit is precisely the current cylinder. The density of misfires was increased (for example, 10 .. 20 events after driving session of 30 .. 60 minutes), but it was not such critical to perform some repair works.


Besides – what to repair? New injector, new spark plug, and also new ignition coil installed in the current cylinder!


As the adaptations are correct, no other injector is leaking – another cylinder neither could be blamed.

What could be the reason in this case?

  • defective injector. Its beam is too close or too far from the spark plug and the fuel mixture of Stratified charge is either too lean in the area of the spark plug or pours off it (the spark plug);
  • defective OEM (BMW) spark plug;
  • faulty Bosch ignition coil. The ignition coil purchased from Bosch dealer – there is no doubt about its origin.

All scenarios sound very unlikely.


It was time to replace the spark plugs again. Here, some images!

Insulator of the spark plug:


Ignition coil:

Obviously, during the replacement of the spark plug, a drop of oil got directly on its insulation. Yes, clean oil is an insulator itself; it does not conduct the current. But by the color of the burns, we can see that it was used oil. Dirt in it is an excellent conductor of current. And it is the cause of the defect described above.

Cause of the problem – either dirty key or oily hands/gloves.

The essence of this entry: N43/N53 series engines have totally different requirements of the culture of the work than engines of the previous generation! The voltage of the ignition system is 2 .. 3 times higher, power of the spark – 3 .. 4 times higher. As you see, even one drop of oil causes serious problems!