A6 stop start fault.

[philipharmes]

A trickle charge over a couple of days will be perfect.
That will top the battery up to 100%.

Stop Start systems only alow the battery to charge to 80%, then the last 20% with charging during braking.

If you still have a problem after a trickle charge, it will probably require a new battery.

[Mikey79]

Bloody thing is driving me mad. I bought a charger and charged the battery over a full day (8am to 9pm). On the run to Devon, stopped after about 130 miles, with lots of regen charging. Got back in the car to carry on and the same thing happened. Took 4 attempts to get it going. On the 4th attempt, I had to really rev it keep it from conking out again. The rest of the journey was fine, no probs.

Since being in Devon, for 5 days it's been fine, having done some shorter journeys (10 miles) and longer (40 miles). After a 30 mile drive today, and being parked up for 2 hours, the same again, multiple attempts and then having to rev to get it going.

I called Audi as it had been in for a service a few weeks before and they said there were no fault codes recorded. Looks like it'll be going back in when we get back.

[Mikey79]

Another update on this. The car has been okay for a few weeks, then it happened again. Took 5 attempts to start the car and keep the engine running/idling around 1000 revs. With each attempt, as usual I press the break pedal, press the start button, it turns over and starts (the rev needle sweeps round to the top and back to 1000), then just cuts out. If I move the gear lever to reverse or drive, I get the Start/Stop system fault notification and need to manually restart the engine. I've got this on video but not in Youtube format so not sure how to go about attaching it to the thread....? Based on what I've read on this thread, I took it to Kwik Fit for a battery check, and they said it's in good condition and would benefit from some long runs. I've also put it on charge (mentioned in a previous post) over 13 hours. Since then I've run it through the diagnostic modes on the charges and nothing of note identified on each of those tests so I'm conifdent the battery is in pretty good shape.

I still have an extended warranty for a few months so took it to a local VAG specialist. They ran all the diagnositcs they could, no fault codes, no errors stored, nothing. Checked the battery and that was fine. And on each attempt they tried to replicate the problem, it started first time, no bother. Took it out for a few runs, no problem. They advised that good practice on start/stop cars is to press the start button without having your foot on the pedal, let it do it's sweep, then press the pedal and start normally. This has never been a problem on this carpreviously, or my C6 Black Edition I had for 3 years before, but I've taken it on board and am trying it with each start

Today, I've just driven about 10 miles and parked for about 90 minutes. Got back in the car, pressed start, it did it's sweep, pressed the pedal and pressed start again, and it barely turned over before just cutting out. As usual, the dash remains on, MMI display is fine, it's the engine won't start. Moved the gear selector to reverse to see if it would get the engine to start and got the error message and to restart manually. I did it again and got the same outcome. On the third time, it turned over and started, I revved the **** out of it and it moved to reverse quickly. I drove home with no issue. Even stopping at lights, the start stop works perfectly - as soon as I take my foor off the brake, it's starts back up again in an instant, no problem. Again, no error lights, fault lights or anything, just the message on the dash. It behaved almost as if it was a flat battery.

The garage said next time it happens just bring it in - sods law it's at 8pm but will try and get it in to them tomorrow. If anyone can advise on how to upload a vid - it's about 1 minute long - it might give a better idea!! Driving me nuts...

[Tripletrouble]

That's a really odd one. Maybe a fault in a loom somehwere?

[Mikey79]

I actually managed to get it back to the VAG specialist round the corner late yesterday afternoon. Plugged it in again and showed no fault codes. I was able to speak to the tech though, and show the video I had where it took 5 attempts to start and he had a few ideas. Suggested a faulty brake pedal sensor - tested it while plugged in, and it seems to be the case. Really intermittent in that, out of 7 presses on the brake pedal, 6 times it showed up that the brake was engaged, once it didn't. So it would seem that's the culprit. The part is ordered and should hopefully be fitted early next week.

Whilst I was waiting, the owner was talking me remap options - Revo stage 1 to take mine from 444bhp to 560!! Bloody expensive but has certainly got me thinking.....

[Elansear]

560bhp wow. That will be impressive, if it decides to start..... good luck.

[Mikey79]

560bhp wow. That will be impressive, if it decides to start..... good luck.

Well, that's the thing hey, get the damn thing working properly first!!! IF, I could afford it (and that's a very big if, by the way!!), I've never had any kind of mods done so not sure on the implications, both insurance wise and also if they ever have a history of going west and screwing the ECU. I'll worry about it if I can fund it. Will post once the brake switch is done and hopefully the end of the fault.

[Mikey79]

Update on this - sory, forgot to post previously. I had the brake switch replaced locally and all was well to start with but then had 1 instance where the fault seemed to happen again (around a couple of weeks after being in the garage) but since then, nothing. I've been following the technician's suggestion to hit start without my foot on the brake allowing the electrics to their "sweep", then start the engine as I normally would. I don't know whether that has an impact at all, but certainly seems like the brake switch was culprit, fingers crossed.

[Marcdz395]

Yep but fingers crossed not for a while now, mine also cut the engine out and had to manually restart which if in traffic was abit of a nuisance but iv scanned mine and also found no errors and the problem seems to clear up straight away but iv definitely not seen it pop up for quite a few months now.


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What was wrong? How did it get fixed. My did the same thing.

[Mikey79]

Are you still having the problem at the moment? I found that mine only really happens if the ambient temperature is above 15/16 degrees. After having the brake pedal switch done, it didn't solve the problem as it happened months later. I've Googled this to death and this is the best thing I've found:

Intermittent hard or no start on 4.0T S6 S7 RS7- possibly solved

A friend is ex Audi/Bentley/VW master tech. We went through the whole thread and he felt the most likely culprit was faulty HPFP or possible faulty injectors. Plugged it in to vag com and recorded all measured values from cold and warm and couldn't replicate the problem. Only fault code it ever picks up is system too rich (can't remember the actual fault code), but I've noticed that when it does start first time (from cold) there's usually a strong smell of petrol.

I've also spoken to the tech at my local specialist during a recent service. He agreed that our diagnosis is a decent one. I'm taking a punt on the HPFP replacement as it's the cheaper of the 2 options and my friend can order from Audi direct at mates rates and fit for me. Injectors is engine out and when I asked at the garage, I'm looking at around £3k minimum in labour alone. Hope this helps!