Rpm drop when revving on neutral / park!!!

[AKRM2C]

Hi Everyone. Just picked up a 2012 BMW M5 F10 with around 26k on the clock.

I have noticed that when the car is warm and it went through the cold start sequence, when i rev it in Neutral / Park, the rpm will drop below the idle point (750 ish) to below 500 (like its going to stall) after revving it to 3000 / 4000 rpms.

However, the ecu usually rev the car on its own yo avoid stalling. this morning, i tried to rev it again, and it actually stalled. Failed to record it.

Does anyone here have any idea what may have caused this? What part should i be replacing? There are no fault codes when scanned. And a local shop suspected it to be the Low Pressure fuel pump under the rear seat.


Car has a catless downpipe, Akrapovic catback, afe intake, and a BM3 stage 1 tune. (stage 1 is tuned before catless downpipe is installed)


I will keep updating this thread. But please if anyone have experienced this, please let me know and tell me what is the actual culprit.

I apologize for my bad english. Thank you bery much!!!

The link below is the gideo where the rpm drop happens but not stalling
https://youtube.com/shorts/D_UL4gITaVs?feature=share

[M5_Raz]

Most common culprits are dirty or bad (rare) MAF sensors. Very easy to clean using something like CRC MAF Cleaner, but make sure they're fully dried when you put them back in.

Let us know if that fixes it.

[JoepM5]

Hi,

I had exactly the same issue a few months back and it turned out to be the engine running too rich due to a faulty HPFP on one of the banks. Replaced both.

Best,
Joep