[VVlasy]

Hey guys,
I have noticed, now for maybe half a year, something that I thought was transmission slipping. But I found out it could be the engine doing something called "bucking".

Usually when I am in comfort, going a slight incline with light throttle (1100-1200ish rpms), I could notice slight dips in RPMs every second or so than can also be felt as a slight jolt, if I applied more throttle, all would be fine. I was thinking all the time it was the transmission or transfer case slipping.

Anyone has any insight on this? It is kinda hard to replicate so I am hesitant ATM to bring it to dealer, until I can safely reproduce this.

SOLVED:

Big thanks go to Robs335iproblems for digging deep and finding the cause

The problem is caused by faulty VANOS actuators (P/N 11367614288 (#11)). There are two of them, one on the exhaust side, one intake. I personally recommend replacing both of them, for the price they are (60$ish) and the effort you are putting in, you might as well do both. Or you can go through data logging to figure out which one it is.

Video guide by mevans

A few tips from me:

• Get a short stubby flathead screwdriver (seen in video from mevans313 ) I had a friend lend me one he has from his dad, probably 30 years old, but for getting out the passenger side actuator is almost impossible without this.
• When you get the actuator turned about a inch-two inches, and it wont go anymore with your hand or the screw driver. Try to pry it off a bit and then keep turning, it will release real easy that way. it took me half an hour to realize this.
• Also be careful not to drop those metal clips that face downwards. Its a real PITA to get back in. Nigh impossible if you have bigger sized hands.

This may also be a solution to a number of other issues, which you might think are coming from the transmission such as:

• Rough 1-2 shift on cold start
• Hard shifts in sport, especially hard in sport+ (feels like stage 3 xHP, without xHP )
• Hard downshifts (mainly 1st and 2nd gear)
• Jerking when applying and releasing throttle (a single jerk, like the engine mounts are bad), very rough in 1st and 2nd gear when torque converter isn't locked, but happens in any gear
• delayed throttle response (bogging on initial throttle)

Please note that some users solved their issues by replacing O2 (lambda) sensors. Also quite cheap and easy to do, so don't give up hope if the actuators don't solve it for you.

[K7]

I've noticed this on my 340i as well. I honestly didn't think too much of it till I read your post.

Is this considered a defect?

[Acheron83]

My M240i does the same thing, but its hard to replicate so I haven't been back to the dealer yet.

[chenry]

Same here

[insanecoder]

I suggest you guys preempt w/ downshift a gear up inclines like I do
you don't want to go low rpms low gear there
I wish my zf would do that but it does everything else correctly and quickly

[DrifterX]

Not sure if I'm experiencing the same thing but while I'm decelerating / engine braking from 1000 rpm to 8-700 rpm (completely off the throttle with the clutch engaged), I get slight jolting every second like the car is rocking back and forth. I think this behaviour has been there all along but I never complained about it or took it in as I assumed it's normal...

[dorkiedoode]

I sorta felt it too, it was a smooth 8 months of driving. I was thinking bmw have a god like transmission or something coming from a long time Honda owner. Guess not anymore...

[B58]

Mine does this also in comfort normal driving. It almost feels like the transmission is slipping for a split second, but i guess its normal behavior based on everyone else posting.

[eksigned]

For the record, mine also does this. Have you driven anything manual before? You'll feel the same thing if you let off the throttle, while in gear!

[riskmaker76]

I would call it surging - I get it to and always have now since I got the car... I can go a couple thousand miles then all of a sudden its there... then gone a second later.. I personally believe its the computer glitching

[petripaa]

Are your cars stock or with some mods? This has to do with gearbox holding gear to too low rpm and either it starts slipping or then engine management is somehow glitching on super low rpms with high engine load.

[VVlasy]

I only have MPPSK, but it was doing it before the MPPSK install

[sttlondon]

my 440 does this as well. straight line, comfort mode, lite throttle (instant mpg usually reads above 40 when its happening). stock car..no mods. my dealership sucks so i've not bothered to take it in but its good to know its not just my car.

[ishowerinjager]

Mine does this as well, I always thought it was the transmission.

[kern417]

same on my 6MT. feels like it's just lurching over and over at low speeds so I try to avoid it as much as possible. but i usually experience it when inching through parking lots.

[BornATeste]

I only notice this when I first start my car up and back out of my parking space. Then I barely touch the throttle in D to get the car moving slowly because I'm in a garage. It reminds me of my dual clutch days in my GTI, where the clutch was hesitant on what the driver wants to do and doesn't know when to fully engage. I know we have conventional automatic transmissions in our cars but the feeling of engagement when it is bucking is very similar to a dual clutch. Has anyone had a dealer try to diagnose this? Seems like our cars would have to be left over night for the dealer to duplicate the issue.

[VVlasy]

I will be getting a new transmission due to a different issue with it. I will be updating this if I notice this bucking with the new one as Well.

For those interested why I am getting it replaced. It is Kicking/jerking at low speeds or when releasing/applying throttle.

[1stAndLastBMW]

I know this thread is old but I wanted to add that I picked up a 2018 M240i PE MT and was completely ecstatic with my first BMW - that is until about the 3500 mile mark when it started exhibiting the "surging". After lots of experimenting, I was able to reproduced often. Conditions:
1. Full Stock M240i Performance Edition ( 5hp + Performance Exhaust )
1. Issue Always between 900-2200 RPMS
2. Always at "slight" throttle ( just enough throttle to keep the car at constant speed ).
3. Driving on an incline ( a decent grade ) brings out the issue and makes it easy to reproduce.
4. Doesn't matter of the speed or gear that I'm in ( 6 Spd MT )
5. There are never any errors or faults
6. Have reproduced the issue even with the cruise control on ( ruling out "user error" or throttle modulation with my foot ).

I have had the car in the deal 3 times. On the 2 visit, the shop foreman did a ride along and after showing him how I was driving the car I had him drive. We were able to reproduce the issue and he noted as such. After it going in, they updated the DME for some recall issue. They weren't able to reproduce after that and gave the car back. I drove the car home and I could not reproduce - until the following day driving to work. Some months later I could not take it any longer. I contacted BMW of America. They opened a case and sent their techs to BMW dealer. I dropped my car and relayed that if they needed help to reproduce, I could be there in minutes. At the end of the day I was given the car back and told that the car is operating as intended. They blew me off as well as the BMWNA rep handling my case.

I'm really disappointed that I found my perfect car - only to have it exhibit these dumb issues AND that BMW basically blew me off. I guess I'm glad that I leased it and it can go right back to where it came from. Too bad, I was hoping I had found a new home for my car habit. Probably getting too old for this shit anyway. Time for that electric car. hahahaha.

[Wires]

Thanks troll!

[StannisBaratheon]

Same issue in my 2016 340ix. Almost feels like a fuel cut. A lot of people experience this so I’m assuming it’s normal. Now if I could just find the source of the howling wind noise that occurs over 30 MPH when my foot is on the gas....

[Supr3me]

I've experienced some surging at low speeds (parking lot speed) usually when the car is a little bit cold. Seems to have been gotten a little bit worse since I started modding and increasing power.
I just chalked it up to the fact that the car doesn't like driving slow lol. That might sound flippant but I don't know how else to put it. If it's happening on a dead stock car, that might be a different matter but for me personally I just take it in stride along with the hard starts, decreased gas mileage, etc.

[RoIIouT]

Might as well add that I have noticed this as well. Typically the car is cold and I am holding the pedal to maintain a constant speed. However, I have never actually seen the RPMs dip when this happens, but I have noticed a "surge" or "lurch". Hard to explain, feels like there is an immense gust of wind from the front for like a quarter of a second.