Code P0174 Bank 2 Too Lean
A few weeks ago, towards the end of a 30+ min drive, my car suddenly started hesitating/stuttering like it was misfiring. It was doing it while on the highway and while idling. Also, quick blips of the gas pedal would make the rpm go so low on the return that it felt like it was going to die, but never actually did.
Checked the code and all I had was P0174 for bank 2 being too lean. I looked at my data on uprev and it was showing bank 2 was too rich, and the voltage for the b2 AFR sensor would fluctuate when the stuttering happened.
- Smoke tested for intake and exhaust leaks — found nothing but a slight leak from the lower b2 o2 sensor and fixed that.
- Swapped the MAF with the one in the other 350Z — no change in either Z.
- Installed a new b2 upper o2 sensor — no change, so I put the original back in.
- Upper O2 harnesses and connectors don’t appear damaged at all.
- Replaced my injectors with a set from a donor motor and replaced the injector harness with a spare I had. Used new o-rings.
Car seemed to be fixed after swapping the injectors. I drove 10 minutes to work with no problem, but on my way home I felt some very light stuttering.
- Performed the idle relearn.
Drove it to work and back again the next day with no issues then I decided to take it on a long drive again. Drove 30 minutes somewhere and on the way back as I was a few minutes from home, the exact same thing as before happened.
- Swapped the upper o2 sensors between banks — issue actually got worse with bank 1 AFR lean at around 18 and bank 2 rich at around 12….
I don’t think it makes sense for a bad fuel filter or pump or a dirty throttle body to be causing something like this, but I’d love to hear if someone has other opinions.
I’d assume I’d have much worse issues (and sounds) if something had happened to the valves or head or bottom end of the motor.
There seems to be a lot of back and forth online about whether or not spark plugs or coil packs could cause this. Maybe the ECU took a shit? Maybe a fuel damper?