[arkie6]

I have a 2008 (build 11/2007) 335i base sedan that is basically stock. I bought the car used with ~70,000 miles a couple of years ago and it now has ~105,000 miles.

It has always had a bit of a stumble when doing a warm engine start. Cold engine starts seem fine, but if the engine is started after being warmed up and after setting 5 to 15 or so minutes, it really stumbles and struggles around 500 RPM for a few seconds, then the speed jumps up to around 1000 RPM and it smooths out, then it settles back down to a normal ~650 RPM. This condition is becoming more noticeable.

A month or so ago I had a cylinder #3 misfire that was isolated to the ignition coil (swapped coil #3 with #5 and the misfire moved to cylinder #5). I ordered a new set of 6 ignition coils. While waiting for parts I decided it was time to replace the leaking valve cover and oil filter housing gaskets, block off the PCV ports in the head, install an external PCV system with oil catch can, and clean / walnut blast the intake valves. The intake and valves had a pretty good layer of carbon buildup and I was hoping that was contributing to my rough idle. I got everything cleaned up and put back together and my rough idle on warm restart persists.

Previously I had an intermittent P0174 bank 2 system too lean code that would come in every few months or so. Now after the intake cleaning I'm getting both P0171 (bank 1 system too lean) and P0174 consistently. I thought initially the engine management system would just need to adapt to the new freer flowing intake tract without all of that carbon buildup, but after driving it a while, I'm not so sure that is the sole cause for the codes.

My code reader freeze frame data shows 700 RPM, fuel rail pressure 4810 kPa (~698 psi), 0% long term fuel trim and ~33% short term fuel trim for both bank 1 and 2 when P0171 and P0174 codes were set this morning.

I'm thinking about the only thing left is partially clogged and/or leaking fuel injectors. My injectors are index -07 and it appears the current version of the injectors is -12.

Is there anything else possibly causing this? I hate to spend ~$750 for 6 new 13-53-8-648-937 injectors and decoupling elements and that not fix the problem.

I have an OBD to USB BMW DCAN cable on order and hope to get the BMW tools software and cable up and running in the next week or so to see if there is anymore troubleshooting I can do before ordering the new injectors.

Thanks for any input.