[SpaceSilver.X1]

I've been here long enough, but I don't recall hearing about this kind of issue.(unless I just missed it) The post is long because I want to include as many details as possible and hope someone can make some sense out of it.


so... I drove for about 700 miles on Monday and Tuesday on a road trip. On I-95 just a couple of hours from DC, it was perfectly sunny with temps around 40. I had driving assist set at 78mph(posted limit was 70mph) most of the way. There was very little traffic. I wasn't not using navigation and the screen was only displaying the music being played on CarPlay.

I was in the right lane, enjoying music and the drive, when the car abruptly slowed down to below 57mph or 58mph, a drop of 20mph. (edit: just wanted add that the car stayed between the lanes, no changes in steering direction) Then it suddenly started accelerating back to 78mph after a couple of seconds. (edit: as if I had floored gas pedal myself... once reaching 78mph, it went back to cruising at a constant 78mph as if nothing had happened) It was unnerving to say the least. I had no idea what happened. There were no cars around me... the road was completely clear with no debris or anything. I kept going thinking it was just a fluke...

but the exact same thing happened 4 or 5 more times for the next 100 miles. At one point, I noticed that a black small "Exit" icon appeared and flashed next to the speed limit(70mph) icon on the lower left of the screen. And sure enough... each time that the speed drastically dropped, the car had just driven past an interstate exit sign. Not really sure what it was doing that.

I decided to pull into the next rest area to see if there was anything blocking the front camera/radar on the grill.. or on the windshield camera? Nothing... the cars was basically spotless because I had just washed and detailed it the day before. Tire pressures were 36 front 32 rear, matching the recommended values of the TMPS screen. There were 3 people in the car and a couple of carry-on cases in the rear. Gas tank was full with Costco gas before I started the trip.

Went to get some drinks and came back to the car. Drove off again.. but the stupid sudden speed drop issue never happened again after the car was restarted. For the next 500 miles, it was trouble-free. (incredibly, averaging 40.8mpg)

I actually stopped by a random BMW dealer at the end of that day(BMW of Fairfax) and asked a couple of techs about it. They said they never heard of such issues(X1 or otherwise). Since I didn't have time to come back the next day for them to diagnose it, I thanked them and left.

Has anyone heard of something like this on the X1 or any other BMW?

Thanks!

[SpaceSilver.X1]

Originally Posted by KosticKen

Were you using your SatNav?

no, satnav was not being used for this trip, since I'm very familiar with those states.

[COOLGREANY]

Originally Posted by KosticKen

Were you using your SatNav?

Originally Posted by SpaceSilver.X1

I wasn't not using navigation (SatNav) and the screen was only displaying the music being played on CarPlay.

No SatNav

[FZI89]

Originally Posted by SpaceSilver.X1

I've been here long enough, but I don't recall hearing about this kind of issue.(unless I just missed it) The post is long because I want to include as many details as possible and hope someone can make some sense out of it.


so... I drove for about 700 miles on Monday and Tuesday on a road trip. On I-95 just a couple of hours from DC, it was perfectly sunny with temps around 40. I had driving assist set at 78mph(posted limit was 70mph) most of the way. There was very little traffic. I wasn't not using navigation and the screen was only displaying the music being played on CarPlay.

I was in the right lane, enjoying music and the drive, when the car abruptly slowed down to below 57mph or 58mph, a drop of 20mph. (edit: just wanted add that the car stayed between the lanes, no changes in steering direction) Then it suddenly started accelerating back to 78mph after a couple of seconds. (edit: as if I had floored gas pedal myself... once reaching 78mph, it went back to cruising at a constant 78mph as if nothing had happened) It was unnerving to say the least. I had no idea what happened. There were no cars around me... the road was completely clear with no debris or anything. I kept going thinking it was just a fluke...

but the exact same thing happened 4 or 5 more times for the next 100 miles. At one point, I noticed that a black small "Exit" icon appeared and flashed next to the speed limit(70mph) icon on the lower left of the screen. And sure enough... each time that the speed drastically dropped, the car had just driven past an interstate [...]

So, I think I may have figured out your issue.

You said you were in the right lane. I’m guessing the furthest right lane that drivers use to exit the highway? And I’m guessing that these exits, where the car slowed down, had corner turns to get off the highway?

If that’s the case, this could explain why the car slowed down. If you check your cruise control settings for cornering, you can choose something between slow and fast cornering. The default is slow.

So if you’re approaching an exit, not using satnav, are on the furthest right line, and have cornering settings on anything other than off or fast (there might not be an off function, I need to check the car), then the cruise control will slow the car down when approaching the exit to perform the turn.

If you’re using satnav and you’re not exiting, then it won’t/shouldn’t slow down.

[SpaceSilver.X1]

Originally Posted by FZI89

So, I think I may have figured out your issue.
.

I think you have solved it for me.

from what I remembered, those exits were in a straight line as the highway.(like the red arrow in the pic below) If I wasn't exiting and wanted to continue on the highway, the car actually had to steer toward the left.

my guess is that the car's cameras detected the "Exit" sign on the right and couldn't decide if I was going straight(red arrow, towards the exit) or continuing on the highway(green arrow). So it probably picked exit first and slowed down, but then changed its mind and realized that I was staying on the highway, so it accelerated back to the original 78mph speed.

at least it's not a glitch or defect... probably just the camera and the car computer unable to decide which directly I was actully going. . although, I believe I do have the curve speed set to "fast"... but I'll check tomorrow when I drive.

Thanks!

[FZI89]

Originally Posted by SpaceSilver.X1

I think you have solved it for me.

from what I remembered, those exits were in a straight line as the highway.(like the red arrow in the pic below) If I wasn't exiting and wanted to continue on the highway, the car actually had to steer toward the left.

my guess is that the car's cameras detected the "Exit" sign on the right and couldn't decide if I was going straight(red arrow, towards the exit) or continuing on the highway(green arrow). So it probably picked exit first and slowed down, but then changed its mind and realized that I was staying on the highway, so it accelerated back to the original 78mph speed.

at least it's not a glitch or defect... probably just the camera and the car computer unable to decide which directly I was actully going. . although, I believe I do have the curve speed set to "fast"... but I'll check tomorrow when I drive.

Thanks!

Amazing! Hopefully this is it!

Come to think of it, even with fast cornering set, the car will have to slow down to some extent 🙈

[John27]

Experienced something not too dissimilar which was really unnerving the first time it happened. Was on a UK 'A' road which was a single lane in each direction with a speed limit of 60mph. Using cruise control (was Sunday morning and no other cars around) when the X1 suddenly dropped to around 40mph. Took me a few moments to realise it was because there was a bend up ahead. While I would have reduced speed for the bend, I wouldn't have normally done so that early or by that amount. Noted it also does the same thing for roundabouts. Most annoying.

I like adaptive cruise control, that is slowing the vehicle down if there is a lower moving vehicle in front etc, but assisted driving is unsettling. I haven't looked yet but I am hoping I can turn off the assisted driving element in the settings somewhere? If anyone has already done this, grateful for a heads up on how to do it?

[SpaceSilver.X1]

Originally Posted by FZI89

Amazing! Hopefully this is it!

Come to think of it, even with fast cornering set, the car will have to slow down to some extent 🙈

tried it on similar highways today, but the issue didn't happen no matter what I tried...

I was just thinking about this yesterday... there's an even bigger safety issue here... when it happened to me earlier this week, I wonder if the rear brake lights came on when the car decided to slow down suddenly by more than 20mph. at the time, there were no cars behind me. if there were cars and they didn't see brake lights, they could have very well rear-ended me?

[FZI89]

Originally Posted by SpaceSilver.X1

tried it on similar highways today, but the issue didn't happen no matter what I tried...

I was just thinking about this yesterday... there's an even bigger safety issue here... when it happened to me earlier this week, I wonder if the rear brake lights came on when the car decided to slow down suddenly by more than 20mph. at the time, there were no cars behind me. if there were cars and they didn't see brake lights, they could have very well rear-ended me?

I’ve tested the action of the brake lights when using the driving assistant a while back and can confirm that they do turn on when the slowing down, especially when going to a lower speed limit