Hey all, I’ve got a 2012 BMW 128i (N52, auto, 63k miles) and this thing has been driving me nuts. Ever since I bought it, it’s had a persistent 2A7C (VANOS inlet, cold start) code.
Current symptoms:
- Rough idle all the time (cold or warm)
- Noticeable hesitation/shudder while driving
- After driving a bit, I end up getting misfire codes on all cylinders
- But the only code is always 2A7C
I’ve gone pretty deep on this already:
- Fixed all oil leaks
- Fresh 5W-30 oil, oil pressure tested good
- Cleaned the VANOS filter screens
- Tested VANOS solenoids → replaced both with OEM anyway
- Replaced spark plugs (OEM), coils are OEM as well
- Replaced both VANOS cam gears with brand new OEM units
- Did the valvetronic relearn
- MAF cleaned and seems fine
At one point I had some exhaust-side VANOS codes, but those went away after doing the solenoids. I even took it to a BMW shop without telling them what I thought, they came back saying cam gears too. So I felt good about that… until I replaced them and literally nothing changed.
So now I’m sitting here with:
- Same exact 2A7C
- Same rough idle
- Same hesitation / misfires
Things I haven’t done yet:
- Haven’t replaced the eccentric shaft sensor
- Haven’t smoke tested for vacuum leaks yet (planning to)
At this point I feel like I’ve thrown all the common VANOS parts at it and got nowhere. Where would you go next on this? Is there something I’m missing on these N52s? Sensor issue, wiring, eccentric shaft sensor, etc.? Any direction would honestly be appreciated. I feel like I’m close but just not seeing it.