[ZaraGSPBMW]

I need feedback and advice from the group on an issue I’ve had recently.

Issue: Acceleration hesitation or stall while progressing through gears 3 to 5 and in the 5k-6k RPM range under a WOT. I wouldn’t classify this as turbo lag. Only experience this issue sometimes, not every time, and cannot predict when or how it will happen. Occurs in Sport Plus, Adaptive, and Eco Individual. Haven’t tested under comfort and other settings, but assume it will occur. Can occur from a standing idle start or while moving—that is, accelerating rapidly from a standard speed limit to a quicker pace. To continue acceleration, I must manually click the gear shifters to continue progressing to the higher gears.

Equipment: 2020 M340i stock with Burger air intake and oil catch can. No specialized or after-market tune. Current OD, 24k miles—sat in the garage for nearly three years of the Pandemic and added less than 5k miles from March 2020 to September 2022. It’s my daily driver, not tracked, well kept and maintained. Hand washed and spoiled rotten. Received every scheduled service on time by the dealer's BMW-certified techs.

Frustration: I dropped it off at the dealer for scheduled service last week and added two items to their “to-do” list: This acceleration issue and fixing the damn sun-roof rattle. Got the car back after the dealer had it for three working days and an opportunity for numerous road tests. Here is what I get told, “The hesitation is normal.” Basically, I’m told by the SA that the tech reported that it’s normal because the car is anticipating that I am going to corner and thus is holding back on giving me full power. I absolutely refuted this preposterous notion. The car has some mysterious AI (my word, not theirs) ability to anticipate my moves and respond and react to me. Obviously, the techs ran diagnostics, and there were no fault codes were reported.

Request: Has anybody experienced this same or similar issue? What did you find out if you had it looked at for this issue? Is anybody experiencing this now but not had it looked at? My concern is that this is the start of something major. This is not my first BMW; I’ve had others—I’m a middle-aged professional and have been driving BMWs since the mid-90s, so I know these cars, and I’ve never had this type or similar issue.

[Assassin]

Sounds like a fuel issue to me. Momentary shortage of fuel on throttle opening / WOT or wrong air/fuel ratio.

The first thing I would is check the sensors fitted to the intake and make sure that they are all seated correctly.

Then put the standard air intake back on the car. Some custom intakes due to their different diameter / shape can adversely effect the accuracy of the MAF / boost sensors and thus the mixture.
Despite the sensors working correctly (so no codes) they may be sending the incorrect readings for fuelling.

Not sure if the petrol engines have any of the plethora of vacuum pipes for turbo actuators that the diesels have as they can cause similar issues if there are any leaks.

Hope you find a solution soon.

[johngetter]

Previous N54 I owned had symptoms you're decribing and it was a faulty fuel sensor. Once it got to a certain RPM during WOT it would buck a little and refuse to keep going.