Low speed - short loss of power - anyone else?

[swamp2]

I have noticed the first glitch in my car.

When accelerating at low speeds, 1st or 2nd gear, in a pretty non aggressive fashion I have noticed a feeling like throttle controller completely lifts the throttle for a split second. I think it has only happened 3 or 4 times (in nearly 4k mi) but now I'm sure it is real. The loss of acceleration is very easy to feel. No idea if it is a DCT specific issue or not. Seems likely it could be. I can not be sure but I think it may occur during a slight lift/reapply to the pedal which may be "confusing" the DCT or throttle control or both.

Anyone else notice this in a 6MT or in a DCT car?

Sorry T-Bone not to put this in your thread but I really thought it would just get buried there.

[rvacha]

My experiences sound similar to yours, but probably not the same. I have narrowed down the conditions needed to make my issue occur. If I start off from a stop and don't spool up the engine enough while letting out the clutch, the RPMs will drop below the idle RPM (naturally). When this happens its as if the DME simply ignores my right foot completely and works on getting the RPMs up to idle (so far that sounds like a decent strategy for a car) BUT even after it has recovered it ignores the accelerator pedal. This can put you in scary and dangerous situations to say the least. The car will not "go" until after I've taken my foot completely off the accelerator. Then, when I depress it again it will accelerate as expected

[J08M3]

There's been a couple random occasions in my 6MT car when I've stepped lightly on the gas pedal to accelerate up from 2K RPMs and it seemed to almost lag, or not really accelerate like it should. It's kinda weird, I couldn't figure out if it was the car or my imagination since it's only happened a couple of times.

[sg///M3]

I've had something similar happen, but only a few times. Usually in 1st gear when accelerating "spiritedly" in the lower "D" mode settings (1-3). There's a little hesitation in the middle of the RMP range. It almost feels as if the computer can't decide whether to shift to second gear or continue accelerating in 1st. Definitely makes the car jerk, though.

[lucid]

I had similar experiences (not as extreme as some have described), but I had written it off to traction and MDM although I didn't see the DSC light flash. I was about to post the question: does the DSC light turn on at every single bit of DSC intervention? Is it a binary thing or is there a threshold for the light to come on? But it sounds like this issue might be caused by something else.

[sg///M3]

Originally Posted by lucid

I had similar experiences (not as extreme as some have described), but I had written it off to traction and MDM although I didn't see the DSC light flash. I was about to post the question: is the DSC light turns on at every single bit of DSC intervention? Is it a binary thing or is there a threshold for the light to come on? But it sounds like this issue might be caused by something else.

I believe the DSC light turns on every time DSC kicks in, regardless of how brief. I may be wrong, though.

[DonM3]

I'm having a similar type of problem with my DCT car. In manual mode and under the moderate acceleration in 1st gear the car surges foward then slows and then surges foward again. This produces a 'bunny hop' experience in the car. I thought it was the DSC cutting in or something, but no light comes on.

[RealSanaii]

Maybe they secretly put a small turbo in there...and with the power button, the turbo is disengaged....

[mkoesel]

Originally Posted by sg///M3

I believe the DSC light turns on every time DSC kicks in, regardless of how brief. I may be wrong, though.

Can't comment on the E9x M3 but I can say that both on my E46 M3 and my E90 335i the DSC does sometimes kick in with no flashing light. As we know, DSC is a complex system and uses many of the car's subsystems in tandem. I think that under some specific combinations of input, the light does not actually flash. For example, the light seems to always occur when cutting throttle but not always when applying braking on a specific wheel; based on what I can feel anyway. Just my observations.

swamp's issue does not seem DSC related, but I suppose it could be, if DSC were overreacing for some reason. I suppose one way to test would be to try to nail down how to to repeat the issue (like rvacha seems to be able to do with his car) and then switch DSC to off and try to duplicate.

[Epacy]

One thing I kinda noticed was that during spirited driving from 1st to 2nd, when the shifter will actually go into 2nd during quick shifts, and step on the peddle there seems to be this slight hesitation when second engages and you try to accelerate.
I really have only noticed in one spot on my trip home on a slight uphill left turn from a stop sign after getting off the highway. Fairly peculiar.

[valeram]

Originally Posted by RealSanaii

Maybe they secretly put a small turbo in there...and with the power button, the turbo is disengaged....

Damn that turbo lag.

I cannot chime in because I am still waiting for my car but I noticed the same thing with my E92 335i, MT. That bunny hup as mentioned. It happened as you disengaged the clutch and press the pedal immediately but it seldom happen and only during a cold start in the morning. Maybe it is something to do with the ECU figuring out on the right parameters to have an optimum fuel mixture. It is just a gues and I don't know because I am just a messager and please don't shoot the messenger.

[footie]

Originally Posted by swamp2

I have noticed the first glitch in my car.

When accelerating at low speeds, 1st or 2nd gear, in a pretty non aggressive fashion I have noticed a feeling like throttle controller completely lifts the throttle for a split second. I think it has only happened 3 or 4 times (in nearly 4k mi) but now I'm sure it is real. The loss of acceleration is very easy to feel. No idea if it is a DCT specific issue or not. Seems likely it could be. I can not be sure but I think it may occur during a slight lift/reapply to the pedal which may be "confusing" the DCT or throttle control or both.

Anyone else notice this in a 6MT or in a DCT car?

Sorry T-Bone not to put this in your thread but I really thought it would just get buried there.

swamp,

Thank you for noticing this as the car with the M-DCT I test drove the owner/sales manager of the car apologized that the car was suffering what you are describing. I might add that I didn't notice this, probably because I was unfamiliar with the car but it's interesting to see this is a fault that is not a one off.

P.S.
They had connected it to the computer in the workshop and zero faults. Hopefully BMW might has a software fix for this soon.

[J08M3]

I was wondering if it was DSC but wasn't sure cause the light never came on any of the times it happened. Unless the light isn't supposed to always come on?

[rvacha]

Originally Posted by Epacy

One thing I kinda noticed was that during spirited driving from 1st to 2nd, when the shifter will actually go into 2nd during quick shifts, and step on the peddle there seems to be this slight hesitation when second engages and you try to accelerate.
I really have only noticed in one spot on my trip home on a slight uphill left turn from a stop sign after getting off the highway. Fairly peculiar.

I have seen this too, even on flat straighaways. Presently I suspect it is the DSC kicking in even though the indicator light doesn't flash

[AustinGelbM4]

Could CDV have ANYTHING to do with this? CDV "issues" typically are more noticable in 1st or 2nd gear changes. I don't know why I can't shake the idea that CDV is somehow at fault. Any ideas?

[mkoesel]

Originally Posted by lurks

Could CDV have ANYTHING to do with this? CDV "issues" typically are more noticable in 1st or 2nd gear changes. I don't know why I can't shake the idea that CDV is somehow at fault. Any ideas?

swamp has a M-DCT which I doubt has a CDV (or CDVs I guess it would be) since the computer is completely is control of the clutch actuation.

[rvacha]

Originally Posted by lurks

Could CDV have ANYTHING to do with this? CDV "issues" typically are more noticable in 1st or 2nd gear changes. I don't know why I can't shake the idea that CDV is somehow at fault. Any ideas?

CDV doesn't control engine output, only the rate at which the clutch can engage. And Swamp doesn't have a 6MT, so there is no human "error" to control

[Epacy]

Originally Posted by rvacha

I have seen this too, even on flat straighaways. Presently I suspect it is the DSC kicking in even though the indicator light doesn't flash

Good to hear you have experienced something similar to this. When I usually take off from there it is in MDM. I would expect it to allow more play though. Perhaps the car is losing traction over some small pebbles that reside in the center crossover.

[GT3 Tim]

Oh boy....sounds similar to the issue they had with the E55's. They would just die like that....it was a software glitch that they fixed. I hope this is isolated, but time will tell on this one.

For now, anybody that has a hesitation or other drivability issue need to DOCUMENT IT WITH THE DEALER. That is the only way they will be alerted to an issue. If they get 500 people complaining about the same thing, they will look into it. I fit is only oone or two here or there, they prolly will not.

So, all of you guys that have any drivability issue need to take it in to the dealer and have it documented! Please, for the sake of ALL of us. The sooner they think there is an issue, the sooner they will be working on a fix.

[MDCTFTW]

Sounds like DSC. Try turning it off and see if you can replicate the problem without blazing up the tires. Haha.

[swamp2]

Good comments. Clearly multiple driveability issues being discussed here. It does seem clear that others have experienced exactly what I posted about. I am positive it is not a DSC issue in my case, way below any limits of traction or slip. Glad to hear that it likely is not M-DCT. I need to go the the dealer anyway. I will tell them they are not likely to reproduce it but hopefully they will document it. Sounds to me like something BMW already knows about and we are all just waiting on v2.0 (or whatever the next version is).

[Hans Delbruck]

Originally Posted by Epacy

One thing I kinda noticed was that during spirited driving from 1st to 2nd, when the shifter will actually go into 2nd during quick shifts, and step on the peddle there seems to be this slight hesitation when second engages and you try to accelerate.
I really have only noticed in one spot on my trip home on a slight uphill left turn from a stop sign after getting off the highway. Fairly peculiar.

E & rvacha,

This sounds very much like the Clutch Delay Valve. As if the clutch slips even though the gear is fully engaged, and you get a momentary lack of acceleration... it only happens when you're really on it (pedal to the floor) and shifting quickly? CDV removal should fix this.


http://www.zeckhausen.com/CDV.htm

(Obviously that is a different issue than swamp is feeling)