Speed limiter issue.

[sjb993]

My car is a September 2021 build G20 M340i MHT (pre LCI) with 30,200 miles on the clock.

My car intermittently performs a kick-down and accelerates whilst cruising at the speed set for the speed limiter, without my foot moving on the pedal. I always drive with the limiter set to adopt the current speed limit, and I have set it to have a +2mph tolerance up to 40mph, and a + 4mph tolerance beyond that. I am certain my foot doesn't move enough to cause the kick-down, and the current speed limit display on the dash which is, I assume, the speed that the limiter uses, doesn't increase.

Firstly, has anyone else experienced this behaviour?

Secondly, I would be very grateful if someone would explain how the kick-down mechanism works as I'm beginning to think it may be faulty.

Many thanks.

[Drmarkf]

I use the speed limiter a lot, in the same sort of way you describe, and especially on crowded motorways and to stay within 20 limits.

I’ve never driven a G3x, but I’ve done a lot of miles in my F31 320d for the past 6 years, and maybe a thousand in a friend’s F30 M340i a few years ago, and I’ve never experienced behaviour like that.

I find it difficult to believe the late model would normally do something different.

[Gassmi]

That's not common on the G20.

Kick-down is a physical click switch at the very bottom of the pedal - you have to push past resistance to trigger it. If your foot isn't moving, it shouldn't happen.

Likely a faulty pedal sensor or the switch itself sticking. The limiter not changing means it's not a camera/sign error.

Get it to BMW while it's still under warranty - 2021 with 30k should be covered. It's a safety thing, don't ignore it.

[drdino]

Floor mat out of the way/not on the pedal at all? I'd get it checked out for sure as it shouldn't behave that way at all.

Have you tried turning off the automatic adoption of speed limits and seeing if the issue reoccurs?

[sjb993]

Thanks for the responses, I'll get it checked.

[Billy_Rosewood]

Fairly certain our f30 will accelerate passed the limiter if the rate of acceleration is high enough.

I also find, whenever I use the limiter, my foot eventually moves further as the journey goes on. Are you sure this isn't the case for you? Every now and again back off the throttle a little and you'll know if the speed decreases or remains the same (and therefore your foot was buried more than you thought).

There's a point in which the throttle is pressed hard enough it'll ignore the limiter and carry on.

The car doesn't need you to press the throttle hard enough to activate the little button under the throttle pedal either.

[sjb993]

Thanks, I'll try that. I'll still get it checked, just to be on the safe side.

[Wills2]

An un-commanded kick down event in a powerful car like the m340i would be alarming and highly dangerous are you sure that's what you meant to describe, or is the car slipping into a lower gear because your foot is applying enough pressure for the car to think you want to accelerate?

[sjb993]

I'm as certain as I can be that my foot doesn't apply more pressure. As soon as it kicks down I take my foot off the pedal and it immediately changes up to higher gears and the speed reduces.

[Wills2]

So it reacts to your pressure change when you lift off? But it kicks down (drops to the lowest usable gear) on its own, if it was my car I'd be driving it straight to the dealer as that isn't right at all. (probably had 10 auto BMWs with the lim button)