Almighty Lean Codes

[NOUD]

Hi,

I have 2005 X3 with 130K miles. Few month ago I got P0174 and P0171 codes. I watched a lot of youtube guides and read forum. Looked simple but I cant get it fixed.

Car runs perfect. Codes appear even if car is just idling. (I guess fuel pump and injectors are fine?). Replaced Desa valce o ring, manifold gaskets, pcv valves and tubes, intake hose has no cracks, since it has no idling or driving issues I guess MAF is working good ( I expected MAF sensor to cause some hesitation). Then I thought maybe O2 sensors, but isnt it odd for O2 sensors to go bad on both banks at the same time?

At this point I have no more ideas of what might cause it.

[jclausen]

The lean faults are registered thru the precat o2 sensors, that are sampling tithe combustion mixture coming out of the engine and finding to much air, lean mixture. The common practice is to smoke check the intake manifold system and look for leaks over looked is the vacuum hoses under the rear of the intake manifold for the secondary air system

[X3456]

Only you know this or not...Do you have installed the performance air filter? like k&n that could very well be the problem...
You may find this of interest:
https://www.bimmerforums.com/forum/s...php?p=30479985

Sent from my SM-J727T using Tapatalk

[jclausen]

Also so I remember there was an issue with the air filte the right type of air filter had a piece of foam over the paper pleats some after market filters did not come with the foam and that could create issues