Surging RPMs coming to a stop - worse when AC is on

[MalcolmV8]

My car has the DCT transmission and I have a feeling it's a DCT issue but not 100%. It's a 2012 135i. Slowing down to a stop right as you're coming to a stop it feels like the car goes in neutral and the RPMs dip and suddenly they flare up and it's in gear and surges or lurches forward as you come to a stop. Extremely annoying to drive. When the car's cold it doesn't really do it, as it heats up it gets worse and the AC on makes it really bad.

I thought maybe an air intake issue since the factory charge pipe had split at one point and I replaced it with an aftermarket aluminum one. After much investigation I was unable to find leaks there but I replaced it with a completely different brand anyways out of frustration and nothing changed. I've also changed the lower part of the charge pipe that goes down to the intercooler. No changes.

There are no codes related to this or the engine.

Wanted to see if anyone had any ideas before the dealer takes advantage of me

Thanks
Malcolm

[NewDaddyDee]

It’s a DCT issue. Some say SIB 12 15 14 fixes it, other people say it’s not actually the SIB but the adaptation reset(s) that actually does it. Anyway, start searching and reading: you’ll find lots of info on here.

[MalcolmV8]

Originally Posted by NewDaddyDee

It’s a DCT issue. Some say SIB 12 15 14 fixes it, other people say it’s not actually the SIB but the adaptation reset that actually does it. Anyway, start searching and reading: you’ll find lots of info on here.

Interesting, that SIB describes the problem exactly. I have a BMW scan tool. I'll see if it has a feature to reset the DCT adaptation. I appreciate the pointer.

[Lester]

There are posts on this forum recently on the manual transmission swap. This may solve your problem.

[MalcolmV8]

Originally Posted by Lester

There are posts on this forum recently on the manual transmission swap. This may solve your problem.

Thanks I did some searching on the manual swap threads and I think I found what you were referring too. Their suggestion was to reset the DCT adaptation as mentioned above. I will try that today and see what happens.

[MalcolmV8]

I found the DCT adaptation reset in my foxwell tool and ran through it. Start car, put in neutral, parking brake on, test starts. I was surprised at the pretty intense clunking and banging you hear in the trans. If even jerked forwards a little a few times. It then said it was completed. After the exit process, power cycle and restart of the car I went for a drive. It's hard to tell but non AC driving might be better. AC on still had the same surging issue coming to a stop. It's hard to tell if it's better or if it'll adjust and relearn and be better.
I told me wife to keep an eye on it over the next few days and let me know. If nothing's changed I guess per that SIB I likely need to take it into the dealer for a software update. Odd as the car never used too do this.

[zx10guy]

My understanding is both the engine and trans adaptations have to be reset.

[MalcolmV8]

Originally Posted by zx10guy

My understanding is both the engine and trans adaptations have to be reset.

I have nothing too loose trying that. I'll check in the foxwell this evening for the engine option and reset it too and then do trans again and see what happens.

[MalcolmV8]

Ran engine and transmission adaptive reset procedures and it was about the same.
So then I saw a clutch adaptation reset in the transmission section so I ran that. Oh boy that made it way worse
Adaptation on clutch 1 went from 1.91 bar to 1.92 bar and clutch 2 went from 1.84 bar to 1.88 bar. Now it even surges and kicks at you in reverse when backing up and normal driving coming to a stop surges worse than before.

Not sure what else I can do? might be time for the dealer as much as I dislike them.

[zx10guy]

Man that sucks. Thanks for the update.

About a year or so ago, I had to go back to my dealer to have my adaptations reset again due to this very problem. A tech at my dealer had discovered this procedure and I was one of the firsts to report it here as a resolution. It appears I might have to do this every few years. I guess paying $160 every few years is not a big deal to restore drivability. I'm not sure what exactly the tech is doing on their end. I may ask my local indie on if they know what exactly to do as the owners of the shop were actually techs at my dealer.

I was also going to see if I can do it myself with my Thinktool Pros scan tool but I'm not even going to try now.

[MalcolmV8]

Originally Posted by zx10guy

Man that sucks. Thanks for the update.

About a year or so ago, I had to go back to my dealer to have my adaptations reset again due to this very problem. A tech at my dealer had discovered this procedure and I was one of the firsts to report it here as a resolution. It appears I might have to do this every few years. I guess paying $160 every few years is not a big deal to restore drivability. I'm not sure what exactly the tech is doing on their end. I may ask my local indie on if they know what exactly to do as the owners of the shop were actually techs at my dealer.

I was also going to see if I can do it myself with my Thinktool Pros scan tool but I'm not even going to try now.

Well it's good to know they were able to reset yours and make it work. One thing that came to mind was that the various adaptation resets for the transmission do have specifications for oil temp. The general reset of the trans adaptations say oil should be 0-90C where as some of the others said 60-100C. Looking back at my pics I was snapping along the way with my phone for reference I was entering clutch adaptation menus at 57C on trans oil. I assume it had hit 60 before I started or else they error and say sorry not in range. Perhaps I could try it again with a more fully heated trans. After a lot of driving I noticed my trans oil temp settled at 92C. I'll give that one last try as I assume the oil viscosity is different and may result in different adaptation been set.

[zx10guy]

Originally Posted by MalcolmV8

Well it's good to know they were able to reset yours and make it work. One thing that came to mind was that the various adaptation resets for the transmission do have specifications for oil temp. The general reset of the trans adaptations say oil should be 0-90C where as some of the others said 60-100C. Looking back at my pics I was snapping along the way with my phone for reference I was entering clutch adaptation menus at 57C on trans oil. I assume it had hit 60 before I started or else they error and say sorry not in range. Perhaps I could try it again with a more fully heated trans. After a lot of driving I noticed my trans oil temp settled at 92C. I'll give that one last try as I assume the oil viscosity is different and may result in different adaptation been set.

You bringing up the trans oil temp might be very relevant. I did end up waiting a bit at the dealership for the tech to do the reset. Was wondering why it was taking so long so maybe the wait time was due to running the engine till the trans temp got into that specific temp range.

Thanks for going through all the leg work.

[MalcolmV8]

Just redid the clutch adaptation with much warmer fluid, 89C and no different.