Cruise control not maintaining speed going downhill

[DurhamLad1973]

Hi, we picked up my wife's new (to us ) RS3 a few weeks ago and while driving back home we had to go along a road that is notorious for mobile speed cameras so the cruise control was set to 50 mph, jobs a good'un we thought.

After a few miles on this particular road there is quite a steep hill to go down but the car, still with the cruise control on just ran away and before we knew it we were well above the 50 mph limit, 57 mph iirc.

My mate who has a 2016 RS3 took me out in his and we did a back to back comparison going down the same hill near to us and his maintained the set speed, well within a couple of mph but again ours just kept on picking up speed, around 10 mpg over the set speed by the time we got to the bottom of the hill

I've seen on a few other forums that other Audi seem to suffer with the same problem, has anyone on here had similar issues. The car is a 2016.

Thanks in advance.

 

[RichardT]

Cruise control doesn’t use the brakes (I think). So it should cut the throttle going down a steep hill. And also change down for engine braking.
Not sure how eco mode changes things, but it doesn’t use engine braking so would assume that it could run away down hill under cruise control.

 

[AlS3BE]

Mine applies the brakes when speed starts picking up. Same with all the Audi’s and vw I’ve had.
In eco mode it can run up a few mph over as it’s not as quick to react. In any other mode it’s pretty much sticks to the set limit and use brakes and throttle to control speed.

 

[The_Ironist]

I have a 30mph long slow descent which ends with short but steep descent on my journey.

My FL 7 Speed keeps speed well on the lower gradient but would creep to 32-33 on the steep bit if I didn’t take over.

It does seem to have the ability to reduce speed quite hard to try and keep it down, enough to throw me forward in my seat a little sometimes.

Not sure if this is by braking or by shifting up the gears prematurely or a combination of the two.

 

[DurhamLad1973]

My TTS keeps to the set speed, give or take the odd mile per hour, my wife's old M140i would do the same, my old 330i would but the RS3 just runs away, way over 10 mph .

I've read software updates might solve the problem but who knows, think it needs to be booked in to the centre we got it from.

 

[Ron240]

With cruise control on my Ford cars it stated in the handbook that speed can increase when going downhill because while it does cut the power it does not apply the brakes.
I just assumed Audi would be the same, but reading the handbook it states that brakes will be applied to maintain the set speed.
That's a new one on me....you learn something new every day.

 

[Joxh]

Just noticed this in mine yesterday. Cruise set at 30 down a steep hill and car reaching 35+

 

[DurhamLad1973]

I've been on a few forums and it does seem to be quite widespread.

 

[Damo S]

Pretty sure mine applies the brakes when its too steep to just coast

 

[kcpism]

Same with my retro fitted CC, usually climbs up a few mph, have to manually keep an eye on it. My CC usually kicks in if it goes over 10mph iirc

 

[JohnM100]

Capabilities vary from model to model.

AFAIK the only ones with CC braking option to avoid downhill runaway are those with ACC or EA888 engines (1.8 or 2.0) irrespective of ACC. Don’t know about RS3 though.

 

[B33r]

Mine (2019 A3 35 TFSI Manual) definitely applies the brakes to keep on the set speed, very rarely see it go even 1mph over when going down hill or 1mph under when going uphill. I even use it to brake/slow down for junctions sometimes by reducing the set speed with the cruise stalk.


Sent from my iPhone using Tapatalk

 

[Ormesome]

My Audi Q2 defo applies the brake whilst on CC. I see them light up in the dark all the time. I use it all the time and here in Switzerland it goes from 50km to 80km to 120km and back all the time on the road. I use the CC as stated in post above, to slow down and keep control of speed as the brakes and speed control is very effective. Cant help with your problem but defo need to get that checked out. Mine never goes 1km over the speed set.
I do not have ACC, just normal CC as did my 1.6tdi. A3 which worked in the same way.

 

[Damo S]

Same with my retro fitted CC, usually climbs up a few mph, have to manually keep an eye on it. My CC usually kicks in if it goes over 10mph iirc

mine was retrofitted by audi when I bought it, yet it does brake

 

[kcpism]

mine was retrofitted by audi when I bought it, yet it does brake

Perhaps newer 8V models etc. do as opposed to my older 8P?

I typically use mine on flat/motorway. Ill try and find a hill later and test lol

 

[Peto]

Perhaps newer 8V models etc. do as opposed to my older 8P?

I typically use mine on flat/motorway. Ill try and find a hill later and test lol

No mine 2015 8v do cruise properly.. I think OP's lady had foot on gas as u still can accelerate when u put foot away it correct itself by set speed

 

[kcpism]

Mine uses gears to maintain speed (auto s tronic) as opposed to applying brakes so has a tendency on downward hills for speed to creep up.

 

[JohnM100]

As stated there is model variability. My PFL used bakes and stronic gears whereas others didn’t.

The easiest test is to drive at 70 and engage CC set to 50. If it brakes then good, but if freewheel only - question answered.

 

[Khufu]

my car used to accelerate going down hill under cruise control until i changed the rear ABS sensors for PLA. It now keeps a fairly constant speed by using the brakes (seen glow of the brake lights coming on). My car is a manual.

 

[AlS3BE]

Been testing mine on road to and from work where there are some steep hills and the cc holds within 1-2mph of set speed up or downhill. In efficiency mode it can creep 3-4mph over/under but any other modes it holds pretty well.
Mine is a fl s3 stronic.

 

[Martinbanshee]

My PFL S3 maintains speed on any downhill. I have ACC and can see the brake lights come on down steeper hills.

 

[dolo]

2015 S3, mine does exactly the same, 50mph downhill at the Angel of the North on the A1, if I set to 50 it will be running away at 57-58 by the bottom of the hill, previous A4 would apply the brakes the S3 doesn't

 

[DurhamLad1973]

Me and my mate did a back to back comparison, he has a 65 plate RS3, ours is a 16 plate.

Both set to 40 mph going down the same hill, his held the speed to40, probably went to 41 mpg before you could feel the speed being held back, ours was doing over 50 mph by the time it got to the bottom of the hill.

It's booked into Wearside Audi tomorrow to get it checked out. Hopefully it's something straight forward like a software issue.

 

[Ron240]

It's booked into Wearside Audi tomorrow to get it checked out. Hopefully it's something straight forward like a software issue.

Is it worth your time and inconvenience bothering about it.....unless of course your car is already booked in for a service?

 

[The_Ironist]

Have you got courtesy booked? Bear in mind they may not go inside the car for 3 hours after you’ve dropped it off and if wanting to pick up same day, 3 hours from them in it to you in it, so limited time to investigate in day 1 now. Based on deliveries anyway.

 

[Ron240]

That's the second time on this forum I have heard about this "3 hour" rule and it is baffling to me.
Is all trace of the virus supposed to magically disappear after 3 hours?

 

[AlS3BE]

That's the second time on this forum I have heard about this "3 hour" rule and it is baffling to me.
Is all trace of the virus supposed to magically disappear after 3 hours?

3 hours was how long it can survive on cardboard type materials and certain porous type materials. Suppose any aerosoled virus particles would be more or less dispersed in 3 hours however It can survive on steel for days so the 3 hour rule is a bit BS in my eyes anyway

 

[AllanG]

My Q5 is booked into Audi Southampton next week and, whilst they have got special procedures for dropping off the car, there is absolutely no mention about them not being able to access the inside of the car for a set period.

 

[ukd4v1d]

My 2017 A3 derv brakes with the cruise control, whether it be to hold the speed or if I use the stalk to reduce the speed for a village as an example

 

[DurhamLad1973]

Just a quick update, no courtesy car, not allowed due to obvious reasons. Car is all sorted, software update was all that was required, so now keeps correct speeds going down hill.

 

[m rol]

Any idea on what?? ABS??