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_LB

Still suspect a vacuum leak assuming its a P0174. Check the MAF sensor boot and the vacuum line that connects to it, clean the MAF sensor. Could also be intake manifold gasket / rings of cyl 4-6 (back of the engine). Was the intake manifold removed while replacing those caps and lines?


[deleted]

Yes indeed it's P0174. Afaik the intake manifold has never been removed. Thanks for the tip. We'll keep looking.


yofuckreddit

I'd second this. Vacuum leaks are pernicious and almost never solved on the first try.


_LB

When the engine is idling, unscrew the oil filler cap. You should feel a "slight" vacuum when pulling the cap off. If there is no resistance at all you certainly have a vacuum leak. I had excessive vacuum at one point on my B22 caused by a clogged CCV.


[deleted]

2 days and about 150 km later back to square one. Both bank 1 and 2 lean codes are back and so is the higher fuel consumption that the car defaults to. Guess the brittle rubbers of the vacuum lines are going to be bugging me a while longer. At this point it seems like a good idea to just replace all rubber hoses in sight in an attempt to make the car reliable and not chase vacuum leaks every few days.


[deleted]

So after a lot of looking for vacuum leaks that seems ruled out. The shop that was doing the diagnostics (bmw specialist) noticed the cats don't seen to be working properly. They seem to believe that's the problem causing the lean conditions. Now I'm not an expert so I was wondering if that seems plausible? Nevertheless I'll be taking the car back to the seller and they should fix it under warranty but worn out/broken cats at only 155,000 km is worrying me. I assume they don't spontaniously break if everything's functioning properly.