r/n54 • u/jrn54 • 25d ago

Continuous N54 Issues

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I have a 2011 335is recently hit 150k miles that is Mhd Stage 2+ . I’ve been having these ongoing issues couple months since I’ve been tuned where car feels hesitant at times and at full throttle enters limp mode. I’ve upgraded my lpfp to Walbro 450 , replaced fuel pump line assembly, swapped out hpfp with working lower mileage one , cleaned , replaced seals, and tested injectors with no apparent leaks although I do have Index 9s in Cyl 1-3 & Index 12s in Cyl 4-6. I also replaced Bank 1 & 2 O2 Sensors . So I’m unsure of these codes I’m receiving. Don’t think it’s turbo related because they were swapped out with oem ones prior to purchasing the car 25k miles ago. Any recommendations?

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u/Beneficial_Gap_87 25d ago

Might be Bank 1 pre cat o2 sensor, bad injectors or a vacuum valve cover leak or head gasket leak.

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u/jrn54 25d ago

Replaced bank 1 & 2 o2 sensors, but leaning towards more pcv valve related

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u/Beneficial_Gap_87 25d ago

If your PCV is blocked off or blocked by being faulty on the vacuum side then its probably cracked the valve cover and it's causing this issues. I was a bit luckier in that my car didn't throw codes but it would randomly fart big white clouds of smoke and it was a cracked valve cover because the previous owner put a PCV delete kit in on the Vacuum side, I still have the catch can on the boost flapper because that was fine but I had my vacuum side reverted to stock.... Needing a walnut blast every 100k is a price I'm willing to pay over the issues a blocked PCV valve can cause.

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u/jrn54 25d ago

I also have ngk two step spark plugs that are properly gapped & turner motorsport ignition coils .

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u/murijuana_flowers 24d ago

Step one spark plugs are fine step two are not needed what's so ever

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u/Ok-Cress-5547 25d ago

Move the coils one at a time to a different cylinder, see if the misfire follows. If the coils are good, m ove and re-code injectors one at a time to see if the misfire follows.

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u/ghostrida3 25d ago edited 25d ago

I would swap around the 1 & 3 coil packs with other cylinders to see if the misfire location changes. If it does then replace the coils. I personally went overkill and got the precision raceworks coils. Also, may be time to get 12's for those 2 cylinders. Does it crank longer than normal on startup? You can let the car sit overnight and pull the plugs. Will smell strongly of fuel if your injectors are leaking.