N54 335 bad idle and dies off

[Nas335]

Hi guys

I'm trying to diagnose if my lpfp or hpfp is dieng.. one morning car starts and very bad idle and it eventually dies off. It's not like a bad coil or bad plug it's much worse idle that the car dies off.

Now it starts normal and drives normal also so I have no idea what the issue could be. Any insight or help will be highly appreciated.

I managed to get some logs and I am not sure what to look for in these logs.

Mods:
Catless downpipes
Bms dci
Charge pipe and bov
Mhd stage1+

 

[R.G.]

Looks like you are running ethanol and you shouldn't be with that map. LPFP shouldn't be struggling like that on 91 map. Likely cause of rough starts as well.

Log a cold start and post it

 

[Nas335]

Hi @R.G. thanks for your response

I doubt there's any ethanol in the tank last time i ran eth was 25% and flashed the e25 mhd map and that was in July.. I will log a cold start and post it up

thanks

 

[R.G.]

When you unlock the car with the key fob before doing the cold start log, listen if you can hear the faint buzz of the pump priming for a few seconds. There was an update for the dme that programmed the priming.

It's always a good habit to turn on ignition / turn off AC compressor and wait 5 seconds before turning engine on a cold start.

If still happens after those precautions, then you can assume from log posted that lpfp would be a good place to start. Lpfp @ 45 psi on a stage 1 map at that boost level is too low. Let's see what a cold log looks like before throwing cash at issue tho

 

[Nas335]

Attached is cold start log..

Car had a slight miss fire read codes..

The lpfp does still prime I hear it when I unlock the car

 

[matreyia]

Hi guys

I'm trying to diagnose if my lpfp or hpfp is dieng.. one morning car starts and very bad idle and it eventually dies off. It's not like a bad coil or bad plug it's much worse idle that the car dies off.

Now it starts normal and drives normal also so I have no idea what the issue could be. Any insight or help will be highly appreciated.

I managed to get some logs and I am not sure what to look for in these logs.

Mods:
Catless downpipes
Bms dci
Charge pipe and bov
Mhd stage1+

Run error/fault check to see codes. Otherwise there is no way to know for certain. I use schwaben tool or carly bmw.

 

[Rcboosted2007]

Typically lpfp will say fuel pump plausibility.