Stop start - rough restart issue

[Moonmonkey831]

Hi all,

On my car there is an intermittent issue with stop start. Sometimes on the restart part, the car restarts and jerks forward violently with a real thud (its almost like it tries to accelerate and then the brakes slam on)

Even if I’m pressing no pedals and it restarts (e.g I turn the steering wheel) it does the same.

It feels pretty disconcerting and not sure what it could be and I don’t really trust it at the moment not to do something bad.

Anyone else had the same issue? It’s only done 5k miles.

It’s due to go into Audi next month for a replacement petrol cap actuator spring that seized (which Audi assist had to come out to the petrol station for to open for me) - so I will ask them then but no doubt it won’t replicate it at the time.

Thanks!



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[rtd]

I had that same issue alongside others related to stop/start. The stealer couldn’t diagnose and thus I had to call Audi UK, and only after making a fuss with them did it go back in and they replaced fuel pumps and I think something else. No issues since. I would say let stealer try first and if no joy take it further with Audi UK.


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[wildbore]

I had this issue once, the car restarted and shot forward violently. In my case, I think what happened was that the car decided to restart itself (I was at lights) at the exact same moment as I pressed the accelerator to induce a restart so I could drive off. the combo of it restarting and me pressing the throttle combined to create a false "OK, engine, the driver wants to go and go now!" type signal. the car shot forward violently and I had to stamp on the brakes.

Just a one-off for me. I note you say that it happens when you are not touching the pedals but that seems strange as Stop/Start can only engage when either the handbrake or Auto-Hold are engaged or the brake pedal is depressed - so how can the car shoot forward, unless you have touched the throttle (even inadvertently - it only takes a mild brush of the pedal) to disengage the handbrake (or Auto-hold)?

[Moonmonkey831]

Yep the stop function engages when I press the brake pedal as you describe. I then take my foot off the brake pedal as it is now stopped.

Normally I then lightly tap the accelerator to start the engine and it’s this that then gives a violent restart and jerk forwards.

Also for me, turning the steering wheel slightly also reengages the start function and then same thing happens.

Also start stop works normally without the jerky restart so it’s intermittent at best.

It just looks <beep> as well when you are at the lights and it actually looks like you’ve stalled it!


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[Heden]

I have the same issue. I reported it to the Audi centre where I bought the car. It is a difficult issue to show to the technician as it is, as you say, intermittent. What they did to my car was a reset of the gearbox. This resolved the issue for a couple of months, but it appeared again a couple of weeks ago. The technician who did the reset explained that it is a known fault but that they "all do it".

I haven't bothered reporting it again as I have started to turn off the start stop system when I start the car anyway

[bn8959]

Have you tried with hill hold assist off? The behaviour is different - it restarts as you lift off the brake pedal, so running smoothly by the time you press the accelerator. Also with ACC on it seems to ‘predict’ when the car in front it going to move and starts up automatically (but won’t move it automatic-go has timed out).
I always have hill hold off as I much prefer the behaviour.

[innercry666]

The stop / start in mine came up with a fault a number of times recently. First time the car ran but it didn't feel normal - very rough. It was only a short journey and on restart it was fine. It's going into Audi today so we shall see...

[Markp]

As above. Try turning off the auto hand brake. Stop start works much better in normal mode.

[Moonmonkey831]

Thanks all.

Don’t really use the hill hold /autohandbrake, at least it wasn’t on when these jerks have happened.

Will ask Audi when I take it in and hopefully it will replicate with a tech in the car


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[Tadass910]

Start stop useless never using it

[Eddie555]

Thanks all.

Don’t really use the hill hold /autohandbrake, at least it wasn’t on when these jerks have happened.

Will ask Audi when I take it in and hopefully it will replicate with a tech in the car


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If you weren’t using hill hold assist when the jerks happened then there’s your problem. Because as soon as you lifted your foot off the brake the engine would have began a start sequence and by you touching the accelerator of course the car will jerk.

[Moonmonkey831]

I would agree but this is violent almost mechanical type unplanned jerk. It’s like the car starts, jumps forwards and the brakes get slammed on all at the same time. I’m likely not describing it properly but it’s not something you would expect to experience especially when it doesn’t feel at all controlled.

I’ll try and write down the actual movement and sequence I do when it happens to see if there is anything obvious I am doing wrong.



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[Eddie555]

I would agree but this is violent almost mechanical type unplanned jerk. It’s like the car starts, jumps forwards and the brakes get slammed on all at the same time. I’m likely not describing it properly but it’s not something you would expect to experience especially when it doesn’t feel at all controlled.

I’ll try and write down the actual movement and sequence I do when it happens to see if there is anything obvious I am doing wrong.



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The other thing I don’t get is why you are actually doing what you are doing. If you just want the car to restart whilst you are stationary just gently lift off the brake then hold brake again. You don’t need to hit the accelerator to restart at all. As I already said there lies the problem which is you actually giving the car gas which is what will set the car into motion.

[EmilA]

My car starts itself quite quickly when I lift off the brake. Certainly recommend just doing that and not going into accelerator peda

[Eddie555]

Question. Does your car have pre-sense city/basic? And also does this happen when there is a car in front of you? If both your answers are yes then what is happening is that the car has detected that you are about to accelerate and sees that an impending impact is possible so it hits the brakes.