3-stage manifold swap problems

[trentonsandler]

My car is a 2010 128i with the N52 engine

Last year I swapped my 1 stage intake for the 3 stage, a pretty common mod, following all of the tutorials available and everything including the tune. I ran into some problems late summer, though, after finishing the project where I got a service engine soon light which gave the code that the engine mixture was too lean. I looked into many problems for this before taking it to a dealership who diagnosed two problems. (I left for college and haven't been able to mess with it since).

The first is replace both disa valves on intake manifold, and intake gaskets. This is relatively straightforward and I know how to do this.

The second was to replace the valve cover assembly. I am confused as to how this could be leading to a lean engine mixture, and what part(s) I need to replace it. Do I order the parts that match my engine (N52), or the parts that match my new intake manifold (3 stage)?

If anyone has any ideas/understand more about this please let me know.

Thank you

[brake-fade]

If you remember that when you did the intake there was a PCV hose and valve going from the valve cover to the intake. Maybe it could be pulling unmetered air through a leaking or cracked valve cover. The plastic covers will warp at the very back. Or maybe it is unrelated to the lean mix and is leaking oil. With regard to the cover replacement, the intake doesn't matter. Replacing the valve cover can be a pain. One of my least favorite repairs that I've done on my car... and I've done a bunch over the years.

[trentonsandler]

Thank you for the quick response! I will check that out as soon as I can

[nevetstoj]

Faulty o2 sensor, wiring, exhaust leak? got those codes when I had an exhaust leak.

[trentonsandler]

Codes I got were both banks too lean, DME mixture control, and air temperature control sensor. Valve cover assembly recommendation was from the dealership

[nevetstoj]

Well easiest way to test the valve cover internals is to start the car and pull off the oil cap. If there is suction on the cap (i.e. physically difficult to pull cap off) and the idle changes when doing so, there is an issue with the valve cover.

Have you looked under the manifold where the tubes are? maybe one popped off?

If BOTH banks are TOO Lean, then a "vacuum leak" where air, "unmetered" by the MAF Sensor, entering the intake downstream of the MAF, is the most likely cause.

Otherwise clogged cats/injectors/02 sensors/exhaust leaks/fuel pump are the only other variables.

The manual says the yellow engine light on dash (light only, no notification on obc) is for emissions related faults only.

This thread, with a similar issue was resolved with cat replacement.
https://www.e90post.com/forums/showthread.php?t=1672386

Also, Do you have the actual codes they pulled as it would be helpful?

[trentonsandler]

Thank you so much for the possibilities it could be, I'm gonna have to wait til I'm back home in May to do any physical tests, but I went ahead and ordered an aluminum valve cover and assembly. I figured that is a good place to start and is probably a good replacement regardless of whether it is the problem or not.

For the codes, I scanned them myself, here are the codes I got possibly relating to the problem:

P0174 [0x0174]
System too lean, bank 2
System Too Lean
Status: Confirmed
----------------------------
P0171 [0x0171]
System too lean, bank 1
System Too Lean
Status: Confirmed
----------------------------
2FA3 [0x2FA3]
Status: Test is inhibited by other DTC, Validated and stored in non volatile memory, Validated fault present at time of request
----------------------------
29E1 [0x29E1]
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault has been present during this drive cycle
----------------------------
29E0 [0x29E0]
Status: Pending fault present, Validated and stored in non volatile memory, Validated fault has been present during this drive cycle
============================

These below are in the central module, not sure if they would have anything to do with it
----------------------------
9CBC [0x9CBC]
Status: Test conditions are met, Validated and stored in non volatile memory
----------------------------
9CC8 [0x9CC8]
Status: Test conditions are met, Validated and stored in non volatile memory
============================

Let me know if that helps!