[Elderado82]

I recently bought a brand new 2025 M340i and have had it for about 3 weeks now. In case you weren't aware, BMW has finally added a button to the M340i to turn the auto start-stop function on and off. Here's the problem I'm experiencing: when I come to a complete stop and have been sitting for anywhere from 15 to 30 seconds, the car wiggles. This only happens when driving in comfort mode with the auto start-stop turned off, and yes, the engine is idling at 500 RPM. It doesn’t happen in sport mode or with the auto start-stop on while in comfort mode.

My theory is that the car, for some reason, doesn't recognize that the auto start-stop is off. As a result, one of two things might be happening: either the starter motor is trying to turn the engine over, thinking it needs to, or something with the transmission is causing the system to react as if it's about to restart. I'm planning to take it in for a check-up to hopefully get it fixed since this issue might be damaging the starter motor.

The main reason for this post is to raise awareness and to see if anyone else with a 2025 M340i or M440i is experiencing similar issues with the new Gen3 B58 and 48-volt system.

[peelerec]

Originally Posted by Elderado82

I recently bought a brand new 2025 M340i and have had it for about 3 weeks now. In case you weren't aware, BMW has finally added a button to the M340i to turn the auto start-stop function on and off. Here's the problem I'm experiencing: when I come to a complete stop and have been sitting for anywhere from 15 to 30 seconds, the car wiggles. This only happens when driving in comfort mode with the auto start-stop turned off, and yes, the engine is idling at 500 RPM. It doesn’t happen in sport mode or with the auto start-stop on while in comfort mode.

My theory is that the car, for some reason, doesn't recognize that the auto start-stop is off. As a result, one of two things might be happening: either the starter motor is trying to turn the engine over, thinking it needs to, or something with the transmission is causing the system to react as if it's about to restart. I'm planning to take it in for a check-up to hopefully get it fixed since this issue might be damaging the starter motor.

The main reason for this post is to raise awareness and to see if anyone else with a 2025 M340i or M440i is experiencing similar issues with the new Gen3 B58 and 48-volt system.

Not sure if related or not, but on occasion and not frequently, when cruising around town in MY22 M340i in comfort or eco-pro and then switching to sport, I also have experienced what you claim. It doesn’t happen enough to justify me taking the vehicle to the dealer, but the 4-5 times it’s happened in 40k miles, I would concur with your description. It’s as if the car wants to shut off but doesn’t, so it “wiggles”

[Elderado82]

Originally Posted by peelerec

Not sure if related or not, but on occasion and not frequently, when cruising around town in MY22 M340i in comfort or eco-pro and then switching to sport, I also have experienced what you claim. It doesn’t happen enough to justify me taking the vehicle to the dealer, but the 4-5 times it’s happened in 40k miles, I would concur with your description. It’s as if the car wants to shut off but doesn’t, so it “wiggles”

Wiggles... I know, funny, right? Before, I had a 2021 M340i and never ever did I witness this kind of behavior. Also, this isn't just a once or twice type of issue—it happens a lot. Not every stop, as I have to sit for a bit, but almost every time it's more than, say, 15 seconds or so, she... wiggles

[Manjot14]

could just be the car at a really low idle so it shakes a bit. Maybe something to do with emissions regulations

[ChrisWMT]

I have a 2025 and have noticed as well. My SWAG is actually the the motor regen turning on and off. There is no starter motor, it starts using the motor between the engine and transmission. While the engine is running it likely is being used as a 48V generator.

[G22b58]

I have a 2021, but it does sound like a sudden change of load on the engine. 500 RPM is also lower than mine (idles at 700). The load change could be AC compressor or the "48V generator". See if you can correlate it to the Energy Flow display. If that display works as mine, the engine is used to charge the 48V battery if the displayed charge drops below 1 bar.

[Eastfront]

Mine does the wiggle, just to add another voice.

[cyclicalcoder]

I also experience this shaking! Didn’t really know how to put it into words, but I’m glad I found your post to inquire about it. Glad to hear I wasn’t the only one to experience it. I think your theory makes sense - hopefully it won’t be too big of an issue

[JayCee24]

Just picked up my 2025 M340i the other day, and I also experience the wiggle