Roll back issues with adaptive cruise control.

[lambertia]

All,

My 1 03tsi regularly rolls back on (even slight) inclines when the ACC brings the car to a stop. It will roll back and then the brakes will bring it to a stop.

It some cases the car comes to a halt with a very loud crunch. It sounds as if it's the gearbox bringing the car to a stop. Hopefully I'm wrong there and the crunch is the brakes.

Yesterday the rollback happened and the car rolled backwards THROUGH the brakes. I felt them bite slightly but it kept going back through them. I stopped it myself before I rolled into the car behind me.

I have taken it back to the dealer and there hasn't been any joy yet. They're not being unhelpful they just haven't seen the issue before and I understand that they have to see it happening if it's not a known fault.

Is anyone else having similar issues?

[lambertia]

Thanks for your response.

I'm not sure you understand how the ACC works. It uses the radar to bring to car to a stop and applies the brakes. The car is most definitely not sitting on the clutch. Not in any way shape or form.

[lambertia]

At least I think that's how it works

[lambertia]

At least I think that's how it works

In the manual it clearly states that for a DSG like mine the ACC holds the car with the brakes. This issue occurs on the slightest of inclines. You wouldn't even know you're on a slope (until you roll back). I plan to take it back in tomorrow.

[lambertia]

Relying on ACC to hold the car in position is fraught with danger if the car in front moves across from in front of you and cruise is set at 100kph You might have an interesting experience as you go past him rapidly.

That's not how it works. Once the car has stopped and the 3 second restart expired, driver intervention is required to get the car moving again.

[grtuned]

Roll back issues with adaptive cruise control.

Have you pressed the brakes? If it's rolling back then hill hold assist isn't working I'm sure it will only work if you press the brakes. If your not pressing the brakes at all you will get roll back. Any DSG will do that.
If your hearing that crunch its normal function of abs intervening to bring your car to a stop. If means your very close to the car in front.
Debatable but using acc in traffic is asking for trouble.
Don't get me wrong I love the tech but its like anything electrical there will always be a glitch. And when you least expect it BANG!!! It's like city assist it only works if you take your eyes of the road. It really should only assist when someone slams there brakes in slow traffic.

[lambertia]

Have you pressed the brakes? If it's rolling back then hill hold assist isn't working I'm sure it will only work if you press the brakes. If your not pressing the brakes at all you will get roll back. Any DSG will do that.

The issue occurs when the car comes to a gradual stop behind the traffic in front. I'm not using the brakes and its not a hard deceleration.

I agree that some roll back will happen. But not one metre or more (measured by watching the the reflection of the wheels in a window - half a wheel rotation = ~1M). I think that's excessive.

If your hearing that crunch its normal function of abs intervening to bring your car to a stop. If means your very close to the car in front.

Not likely related to this - I'm going backwards after all but will be less concerned if the crunch is the brakes.

Debatable but using acc in traffic is asking for trouble.
Don't get me wrong I love the tech but its like anything electrical there will always be a glitch. And when you least expect it BANG!!! It's like city assist it only works if you take your eyes of the road. It really should only assist when someone slams there brakes in slow traffic.

ACC can make even Punt Road an enjoyable drive!

I agree that you always need to keep in control. I am at the stage where I brake if I feel the rollback. However I want to follow through in case there is something wrong with my car. I have take off issues as well (unrelated to ACC) which I'll post in another thread.

Hence the question if others are getting significant rollback.

[grtuned]

Hill hold will apply the amount of pressure registered when first operated and continue to maintain that brake pressure continuously every time it activates. So if you only operated the brake lightly then turned on the hill hold every time you stop it will apply that pressure this may be why the vehicle is rolling back even though hill hold has switched on.
My suggestion is turn off hill hold apply a harder Brake pressure then activate hill hold then seat belt on and take off normally so it releases and monitor
See how that reacts.

[zardoz]

I've had the *exact* same issue.. but noticing it more now than I did before.

Interestingly enough, we have the exact same spec car (MY14 wagon 103TSI, limestone grey, roof, leather, DAC). I'll have to keep an eye out on the roads

[pepito]

Are you sure ACC is supposed to actually stop the car?

I've tried it twice (coincidentally on Punt Rd) and I know for certain I'd have run into the car in front if I didn't brake at the last second myself.

Manual GTI here.


Sent from my iPhone using Tapatalk

[GolfVII]

ACC does stop you regardless if auto hold is engaged or not in a DSG. I have not had roll back issues in my TDI. I have noticed on my car the breaks don't disengage until the car wants take off not before.

The only time I had a sketchy moments was when I was coming up to a stationary car and the radar did not see it and another time doing 100 and some bright spark pulled in to my lane doing around 40. Some people do not know how to drive on free-ways.

Any concerns I have had with my car I went back to the dealer and they have fixed it no questions asked, your issue sounds like a safety concern so taking it back to the dealer to inspect should be your first stop.

[AdamD]

Hill hold will apply the amount of pressure registered when first operated and continue to maintain that brake pressure continuously every time it activates.

Actually, I believe that the hill hold assist will apply only the amount of brake pressure that was applied at the moment the car comes to a standstill (which is different for each and every stop). If the ACC is only applying gentle braking force (and less force will be required if the car is decelerating uphill), then that amount of brake pressure may initially be insufficient to hold the car on the slope - hence the initial rollback (followed by an emergency reaction from the car when it realises it's moving backward).

[lambertia]

Actually, I believe that the hill hold assist will apply only the amount of brake pressure that was applied at the moment the car comes to a standstill (which is different for each and every stop). If the ACC is only applying gentle braking force (and less force will be required if the car is decelerating uphill), then that amount of brake pressure may initially be insufficient to hold the car on the slope - hence the initial rollback (followed by an emergency reaction from the car when it realises it's moving backward).

That is a very good theory.

[lambertia]

Are you sure ACC is supposed to actually stop the car?

I've tried it twice (coincidentally on Punt Rd) and I know for certain I'd have run into the car in front if I didn't brake at the last second myself.

Manual GTI here.


Sent from my iPhone using Tapatalk

The manual clearly states that the ACC cannot detect stationary traffic. It will stop you if the car in front slows down and stops. Change the mfd to assist display and see what it's doing.

[agentthumb]

The manual clearly states that the ACC cannot detect stationary traffic. It will stop you if the car in front slows down and stops. Change the mfd to assist display and see what it's doing.

I'm also fairly certain the feature to sop the car isn't present on Manuals. Only available on DSGs.

Cuts out at 30km/h due to the system's inability to operate the clutch in a manual car to stop it from stalling. Also, bringing the car to a stop from 60kmh in 5th gear could be interesting

Automatic Distance Control ACC < Technical Glossary < Innovation & Technology