RPMs go up but car does not accelerate

[M8]

Here's a weird one. If I'm driving in traffic and trying to maintain a constant speed (accelerator pedal barely depressed), I've noticed that the rpms begin to rise significantly but the car does not go any faster. In fact, I was in 6th gear going about 40 and the rpms were around 3500. I find that when it's doing this (doesn't do it all the time), I can modulate the rpms up and down without affecting the speed of the car. It's almost like it's a manual transmission with the clutch depressed. If I get the rpms too high, it eventually realizes what's going on and the rpms drop and my head jerks back from the sudden acceleration.

Any ideas before I go to the dealer who will tell me they can't replicate?

Here's a picture I snapped yesterday. Clearly, rpms way too high for that gear at that speed.

[M6-Coupe]

Looks like DCT or clutch issue ?

[Bönz]

Agreed. Sounds like a slipping clutch, but the fact it can correct itself (in the same gear) is odd. If this is only happening in odd OR even gears, it could be a bad clutch pack. If it happens in odd AND even gears it could be DCT fluid level or pump pressure.

[v3n0m]

Looks like a dct clutch issue. It's slipping. I'd take it in ASAP since it could cause excessive wear on the clutch plates.

[M8]

Hard to pinpoint but it seems to do it in all gears, not odd or even ones. If I do manual (paddle) shifting, it seems to stop.

[M6-Coupe]

Originally Posted by M8

Hard to pinpoint but it seems to do it in all gears, not odd or even ones. If I do manual (paddle) shifting, it seems to stop.

you mean in manual it's working properly?
If yes then clutch should be fine. It's DCT... maybe the TCU (transmission control unit) must be updated or software related issue...

[BwoodBMW]

Wow that is strange....

[Bönz]

Originally Posted by M8

If I get the rpms too high, it eventually realizes what's going on and the rpms drop and my head jerks back from the sudden acceleration.

Sounds like a slipping clutch suddenly engaging. Root cause unknown - but get it checked out.

[RPiM5]

Actually, this is not a new issue. Concordantly, ergo, and vis a vis (matrix movie reference) I don't know if this occurs on later model builds, say anything built after Feb 2013, but I know of at least one other person who has this happen to them too. They never reported if they took it to the dealer or not to get it diagnosed.

I have had this issue on my M5 for over a year and a half now or for about 25,000 miles now, my DCT or clutch still has yet to die. It occurs in both even and odd gears, but it only occurs at low rpms. So if you are driving in D1 mode on the DCT and driving around with the gas pedal pressed lightly, it can be replicated quite easily. But if you are revving it out in S3 mode while driving around, it won't happen. I don't believe that it is an issue caused by a clutch, I believe it is something software related to the DCT. I never took it into the dealer because it's really not that troublesome and I still have warranty. But it I DO in fact experience this every single day on my drive to work. I have to drive at 20mph on the facility where I work and I always drive around in D1 mode to keep the revs down so as to keep the M5 quiet as possible because of my straightpipes. I usually don't want my co-workers to think I'm hooning my M5 around where I work. Lol! I can make a video if anyone is curious as to what exactly is happening with the car if you want. I figure if the DCT or the clutch is going to go bad, might as well let it go bad and then have a legitimate reason for a replacement under warranty as opposed to bringing it in to the dealership and filing a "customer states: that the clutch is slipping" where the tech has to drive my car around and troubleshoot. To which I would probably end up with a wrecked M5 as I have observed the tech's at the dealership hooning my M5 before. So yeah I have extended warranty up to 100,000 miles so I have until then for the DCT or clutch to break. Lol!

[Bönz]

Guys, this is simple and mechanical. For any given gear at a given vehicle speed, the engine should be turning at a constant speed (rpm) - assuming the clutch is fully engaged.

If the gear is constant and the vehicle speed is constant and the engine speed is rising - you got a problem - period.

[M8]

So I really tried yesterday to see what type of conditions this occurs in and here are the results:

Low RPMS (under 2000)
Doesn't matter if in manual shift or auto
Seems to occur most in gears 4 and up (all the way to 7th)
Happens in odd and even gears

If you are accelerating or RPMs are higher, no problems.

I made an appt to bring it in but unfortunately couldn't get a loaner until the end of April so it may be a while.

On a positive note, I gave them the service bulletin for the squeaking brakes and they found it and will perform that service as well.

My personal opinion is it's a software issue and not mechanical. I'm guessing they will re-flash everything and all will return to normal. Alex, I'll be calling you again soon!

Thanks for all the comments/advice. I'll post when I learn what the problem was but I'm dreading the "Could not replicate" excuse.

[ChrisNich117]

Video please! I'm sure we could figure it out with more info.

Actually I think it's the drive logic function of the transmission. You can probably have them reset it at the dealership. Might be acting funky because of how it has adapted to the way you drive the car in automatic mode. That's my best guess. :

[Bönz]

Slipping the clutch is not part of MDCTs adaptive behavior. Assuming this isn't a false reading of the tachometer, if the engine is actually revving and the clutch is engaged, the car should accelerate. If you are in a high gear at low rpm and lugging the engine, you won't accelerate quickly, but you should accelerate nonetheless. This is basic automotive mechanics.

Now the root cause of the slipping clutch could be software, a bad solenoid, a bad pump or a bad clutch (unlikely), but this behavior isn't normal. I'm glad OP made an appointment.

[stealth.pilot]

Agree this is not normal. I've never seen this on an M5.

[M8]

I don't have a video of the occurrence but suffice it to say it would just show the engine start to rev without an increase in speed.

It is definitely not a faulty tach as you can hear the engine rev and then there is an abrupt acceleration where you head hits the back of the headrest. It drives my passengers nuts thinking I just don't know how to drive properly.

One other thing I forgot to mention, sometimes, when I left off the gas pedal, the rpms will oscillate up and down between about 1100 and 1500. Almost like it's going to downshift.

The mystery continues!

[Boss330]

Originally Posted by RPiM5

Actually, this is not a new issue. Concordantly, ergo, and vis a vis (matrix movie reference) I don't know if this occurs on later model builds, say anything built after Feb 2013, but I know of at least one other person who has this happen to them too. They never reported if they took it to the dealer or not to get it diagnosed.

I have had this issue on my M5 for over a year and a half now or for about 25,000 miles now, my DCT or clutch still has yet to die. It occurs in both even and odd gears, but it only occurs at low rpms. So if you are driving in D1 mode on the DCT and driving around with the gas pedal pressed lightly, it can be replicated quite easily. But if you are revving it out in S3 mode while driving around, it won't happen. I don't believe that it is an issue caused by a clutch, I believe it is something software related to the DCT. I never took it into the dealer because it's really not that troublesome and I still have warranty. But it I DO in fact experience this every single day on my drive to work. I have to drive at 20mph on the facility where I work and I always drive around in D1 mode to keep the revs down so as to keep the M5 quiet as possible because of my straightpipes. I usually don't want my co-workers to think I'm hooning my M5 around where I work. Lol! I can make a video if anyone is curious as to what exactly is happening with the car if you want. I figure if the DCT or the clutch is going to go bad, might as well let it go bad and then have a legitimate reason for a replacement under warranty as opposed to bringing it in to the dealership and filing a "customer states: that the clutch is slipping" where the tech has to drive my car around and troubleshoot. To which I would probably end up with a wrecked M5 as I have observed the tech's at the dealership hooning my M5 before. So yeah I have extended warranty up to 100,000 miles so I have until then for the DCT or clutch to break. Lol!

Dave,

If the issue shows up on the diagnostics it will also show how often it happens and at which mileage or time it happened. If you continue to drive with the issue occurring I would be a bit worried that BMW will claim that the excessive wear on the clutches is down to user error (or failing to have the car serviced/diagnosed when the issue first occurred).

I would feel safer if I went to the dealer to have the issue diagnosed. If they can't find the problem at least you can argue that you did go to the dealer with the problem if the clutches ends up being worn out prematurely at a later date.

[RPiM5]

Alright dudes. I don't know if M8 ever got back to us on his experience with the dealer regarding this issue but I just got it solved today on my own M5. Long story short, it was indeed a software issue. The dealership needed to update the entire software on my M5. I've never had a software update and boy was it a big one! Took them over 5 hours to download and install on to my car. I also got my last free oil change and all of my spark plugs changed out today. I'm less than 500 miles away from the big 5-Oh! So yeah after I got the car back I test drove it and the DCT doesn't "hunt" for the right gear to be in any more. The software update did the trick. On the drive back home I could immediately tell that the update changed a whole lot of things. A lot of changes to the iDrive and the entire iDrive system is much faster now. The DCT is also much much smoother now as well and it feels faster too. Maybe I missed it, which is hard to imagine, because I don't miss much, but BMW sure made a lot of changes to the M5 through these updates. Would have been nice if my dealer would've informed me. They never attempted to update my car before. One bad thing though is that all of my custom coding has been wiped. Super annoying, so now I have to find V12 again. Doh! Overall, I think the update was for the better, but one thing I can already tell that I don't like is that BMW changed the graphics in the heads up display for navigational directions. Usually upcoming lane changes were depicted in nice white lanes on the HUD, but now they have this harder to see red graphics that seem more confusing.

[drewmisha]

Dave,

Do you get tire pressure psi numbers now that your Idrive firmware is updated even though all the coding got wiped out?

[RPiM5]

Originally Posted by drewmisha

Dave,

Do you get tire pressure psi numbers now that your Idrive firmware is updated even though all the coding got wiped out?

No I sure do not my friend. Lame how they keep the 2013 M5's in the dark, but the 2014's and 2015's get the good stuff. Lol! Gonna have to get that recoded again.

[nynd]

Dave,
Do you have any info on the software update (is there a bulletin or service #) that one can reference with their dealer?

[Jay-K]

yes looks like a dct clutch issue, get to the dealer asap.
i won't risk driving the car more if that happens.
goodluck!

[RPiM5]

Originally Posted by nynd

Dave,
Do you have any info on the software update (is there a bulletin or service #) that one can reference with their dealer?

No I didn't ask for any specifics. My best advice is to contact your trusted Service Advisor and have them look up the information about the software update(s).