Are BMW 120i's sensitive to source of petrol ?

[V6Alfisti]

My mother in law was having problems with her 2008 120i, I plugged it in and got two error codes

P0175 System Too Rich and P122F BMW Nitrogen Oxide Sensor Binary Oxygen Sensor Short Circuit, with a very rough idle at start up.

I cleared the codes but they instantly returned, a quick google suggested that actually the MAF is often to blame.

So the next time mother in law is back in my neck of the woods, I was going to disconnect the MAF and see if that fixed it

However in the meantime the mother in law popped into a local friendly garage, basically putting some cleaning agent through the petrol system and blaming supermarket petrol.

I know that supermarket petrol is fine but typically has less cleaning agents, are the 120i's particularly sensitive to this? As the petrol cleaner (presumably an injector cleaner) has surprisingly resulted in the car firing up normally with no warning codes.

[Touring442]

A 2008 120i has the lovely* N43 engine. The NoX sensor is very failure prone and 10 years is a good life for one. BMW only, and don't bother with an aftermarket one (NGK etc) as they don't work.

£350 from BMW.

N43's are fickle beats, and some just resist all attempts to fix them, an odyssey of fault codes and chasing your arse trying to clear them. Good luck!

[naturalaspiration]

Sounds like the dreaded injectors issue?

https://www.pistonheads.com/gassing/topic.asp?h=0&...

[naturalaspiration]

Also if the issue is due to the faulty NOX sensor these guys have the NOX emulator:

https://bimmerprofs.com/

Edited by naturalaspiration on Sunday 2nd June 12:27

[V6Alfisti]

Thanks guys, perhaps the dreaded injector issue is related to the cleansing agents in the petrol, who knows.

Good (not good) to know that all of the above issues can cause woes on these cars! I will be suggesting an annual dose of Wurth Injector Cleaner which kept my Alfa GT JTS in fine form (despite a similar reputation for injector longevity!)