525i N53 nox or injectors or whatever

[monsterenergy420]

Hi everybody,

I've been reading the boards for a while and i am looking for your advice.

I got a 525i equipped with (unfortunately) a N53 218bhp engine, which has given me lots of both head and stomach aches in the last few months in this complicated love-hate relationship.

I've been chasing a lean condition but i'm going nowhere.

So far I have changed spark plugs, ignition coils, valve cover, done countless of smoke tests, brought to 100 different garages.

The last one reassured me that they also checked fuel pressure and all was good. The only thing that left me quite confused was that they said injectors were good but "not coded correctly".

So i took the beast for a ride last weekend. Rough idling and misfires I had the past week seem to be gone (for now), however, when i was on my way back home with my Miss I got a CEL that made me spit blood from my eyes.

Long story short: brought the car back to the garage, they scanned it but they weren't able to figure out what was wrong.

The only thing that it's still present is a 2B05 NOx sensor-related error which resists all the adaptations resets.

I checked both long and short fuel trims: short ones seem to be normal, despite long ones appear to be quite high (up to 25-30!) on both banks 1 and 2. MAF reading seem stable between 3 and 7g/s.

Garage suggested to replace the NOx thing but I'm unsure that is the culprit.

To be honest I've read different experiences online but I don't know what to do next since a lot of money was forked out for various stuff already, so I would like to proceed with a good step.