Low speed - short loss of power - anyone else?

[rvacha]

Originally Posted by Hans Delbruck

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)

I had an E39 540i Sport that sorta started the whole CDV rage. I never removed the CDV so I am very familiar with its effects. The M3 phenomonom is different. In the M3 its as if the engine has cut power - you can actually feel it and the engine won't spin up, in fact it may be possible that the engine RPMs actually drop (but I haven't caught glimpse of the tach when it happens so I'm not positive). A CDV issue by contrast leads to a momentarily spin-happy engine and it is easy to tell that the clutch is slipping

[ajj]

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.

.

[Boost3dm3]

i had the same problem over the weekend and was really wierd. Same as others said, I was at a stop sign and tried to accelerate normally in first but car didnt feel like it had any torque or power although once in second everything felt normal. Engine revved up over 3000 and car wasnt really moving all that well. Like the gas pedal wasnt doing anything. Anyone else have this problem? As a side note i did have MDM on for a little while before then turned it off only to experience the low power minutes later.

[lugnut]

Originally Posted by 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 forward then slows and then surges forward 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.

OK, now that you mention this, I remember 2 occasions where I felt something similar to this. I don't have the DCT though, I have the 6sp. I shifted from 1st to 2nd (nothing overly aggressive, shift point is around 4800rpm) and felt a brief loss of power, then the car surged as expected. The car behaves as though it lost fuel momentarily, the rpms drop quickly, then boom...right back to normal. The second time this happened I was in second gear, accelerating up through the revs in traffic (again, not aggressive driving) and it dropped, then kicked back to life in about a second. Both times this occured I was within 5 miles of my home, so I suppose it may somehow (???) be related to a cold engine.

[Boost3dm3]

I think mine was a CDV problem then because it jus kept revving up but speed was not picking up very fast. It was like the gas pedal was held constant even though I was pushing down more and more. Is there such a thing as a stuck CDV?

[Herms]

Originally Posted by 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.

I've noticed something similar a few times in my 6MT, but I've been chalking it up to driver error

[JS11]

i thought the CDV was non-restrictive therefore not a problem after reading eas's buildup journal here: http://www.m3post.com/forums/showthread.php?t=150287
but that leads to the question why is it there in the first place if it serves no function?

[TLud]

Originally Posted by JS11

i thought the CDV was non-restrictive therefore not a problem after reading eas's buildup journal here: http://www.m3post.com/forums/showthread.php?t=150287
but that leads to the question why is it there in the first place if it serves no function?

+1

[satinghostrider]

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.

I notice this when downshifting in auto mode S2 where by you drop to 2nd gear from higher gears and the minute you hit the 2nd gear and accelerate, there is a lag before u go. Quite irritating IMHO.

[footie]

Originally Posted by 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.

Are you sure this isn't just the effects of a sensitive throttle because of the power button, your foot slightly lifting as you accelerate and the brief stopping causing your foot to go back forward on to the throttle causing the process to start again.

[DonM3]

Thanks footie.

Yes it is because of what you described. Driver induced oscillations.

Originally Posted by footie

Are you sure this isn't just the effects of a sensitive throttle because of the power button, your foot slightly lifting as you accelerate and the brief stopping causing your foot to go back forward on to the throttle causing the process to start again.

[bryanr]

I searched for a while trying to find similar experiences. Glad to stumble across this thread.

I've been noticing this when trying to accelerate at a reasonably rapid pace from a stop. Is driver-induced oscillations the final word here? Or is there potentially a software bug.

[JCtx]

Originally Posted by JS11

i thought the CDV was non-restrictive therefore not a problem

Yep, no CDV on E9x M3s. Looks like a CDV, but it's hollowed inside.

[swamp2]

Originally Posted by bryanr

I searched for a while trying to find similar experiences. Glad to stumble across this thread.

I've been noticing this when trying to accelerate at a reasonably rapid pace from a stop. Is driver-induced oscillations the final word here? Or is there potentially a software bug.

1. Driver induced oscillations is essentially a user error.

2. My OP was the beginning of the observation and enormous ensuing discussion on the M-DCT lag. There are dozens of posts on this topic. The shortest answer here is that the latest engine/transmission software goes a long way toward fixing this problem but it is not entirely gone.

3. A similar lag feeling has been found to be caused by the totally separate/unrelated issue of the collapse/restriction of an idle control valve hose. The best discussion of this issue is here.

Hope this helps.

[SenorFunkyPants]

Be interested if some peeps would try this...In third gear at revs 2 - 2.5k slam the throttle open as quick as possible and note the engine response.

[bryanr]

Originally Posted by swamp2

1. Driver induced oscillations is essentially a user error.

2. My OP was the beginning of the observation and enormous ensuing discussion on the M-DCT lag. There are dozens of posts on this topic. The shortest answer here is that the latest engine/transmission software goes a long way toward fixing this problem but it is not entirely gone.

3. A similar lag feeling has been found to be caused by the totally separate/unrelated issue of the collapse/restriction of an idle control valve hose. The best discussion of this issue is here.

Hope this helps.

Gotcha

I have noticed that, at times, when the car starts lurching (what could be initially from DIO), even after my foot is fully off the clutch and my right foot is steady as a rock it keeps lurching a bit and I have to take my foot completely off the gas and rethrottle to go smooth

[mixja]

I haven't noticed this issue, but have noticed if you are between 2200-2800RPM in 3rd gear and very suddenly go WOT, the car seems to back off on the power until around 3500RPM.

If you ease the throttle to WOT or go WOT before 2200RPM or after 2800RPM the car pulls hard...

[SenorFunkyPants]

Originally Posted by mixja

I haven't noticed this issue, but have noticed if you are between 2200-2800RPM in 3rd gear and very suddenly go WOT, the car seems to back off on the power until around 3500RPM.
If you ease the throttle to WOT or go WOT before 2200RPM or after 2800RPM the car pulls hard...

Thats been an issue for a while for UK cars (both manual and DCT) but wasn't sure about cars in other markets. It generally goes un-noticed as its a counterintuitive application of the throttle. I think recent software updates have reduced the effect but its still there.

[swamp2]

Originally Posted by bryanr

Gotcha

I have noticed that, at times, when the car starts lurching (what could be initially from DIO), even after my foot is fully off the clutch and my right foot is steady as a rock it keeps lurching a bit and I have to take my foot completely off the gas and rethrottle to go smooth

One tip: Try pressing your foot against the transmission tunnel for friction. If you do it right it can really help reduce unwanted foot movements and hence reduce/eliminate DIO.