135i strange rpm pulse when quick let off only when warm (logs)

[studio54]

Hello,

my 135i has a strange behaviour only when very warmed up, in sport or "circuit like" driving.
(normal oil temp and minimum 5-10 WOTs or more).

This behaviour get more pronounced as the engine get warmer, and is very much more noticeable on downhill.

I have not this problem when cold or when warming up.


Problem : at any speed, any gear, but not everytime, when i push the pedal (slightly or full) and accelerate a few seconds, then release it quickly, it will buck or jerk but forward, like if i pushed again and released very very quickly the pedal after let off (best description i think), a kind of rpm jump (small pulse),everyone in the car can feel it.

The problem tend to be more pronounced as the pedal course and the throttle duration is short..
If i go to 6500 rpm full throttle, it will not do it.


car: MT 135i with ~60k miles
chronological mod list :
- local dealer tune stage 1
- DCI
[symptoms appeared few days after DCI, but i don't think it's related??]
- ER Chargepipe
- Forge DV (yellow springs)
- MHD Stage 1 or 1+ (only winter)

Here are logs : Datazap log

I tried to reproduce the problem, on this screenshot you can see exactly where the problem occurs.
a small jump in rpm while pedal pos is 0.



any hints? spark plugs?

thank you

[c1pher]

Mine with DCT exhibited similar behavior when I would come to a stop. The idle would rise and then drop. That stopped after I got a Dinan tune. I'm not sure what causes that or if your situation is related. It seems like there is some programming in the stock tune that causes that to happen. BMW said my car was acting normally despite that and the delay in throttle engagement. They completely reloaded the factory programming and didn't solve the problem.

[studio54]

Originally Posted by MGM135is

Mine with DCT exhibited similar behavior when I would come to a stop. The idle would rise and then drop. That stopped after I got a Dinan tune. I'm not sure what causes that or if your situation is related. It seems like there is some programming in the stock tune that causes that to happen. BMW said my car was acting normally despite that and the delay in throttle engagement. They completely reloaded the factory programming and didn't solve the problem.

i have a tune too (local dealer tune and then mhd)

mine does not this when going to a stop, it does not do this at idle , but in the rpm

it seems to do this also when i push the pedal during a decelerration phase to throttle again, a kind of "vooovooomm" , like an hesitation and then it throttle normaly again,
and it happens only when engine is very warm, like after driving agressivly and more often during summer !

and no codes...

i probably have to change the plugs ??

[studio54]

update:

all 6 coils (bosch) and spark plugs (bosch) changed, problem resolved