start - stop (or rather not)

[ti rich]

My start stop system appears to have a mind of its own and fails to stop say 50% of the time even when the engine is fully up to temp.

Is anyone else getting this?

[Guest 2]

Sorry to be blunt, but are you doing it right?

Ie, neutral, clutch out and footbrake on? Also, it wont engage if the car is on a certain degree of incline.

Thats the way the A4 courtesy car I have does it but the A6 might be different

[ti rich]

Yes, i believe i am doing it right......but the car isnt!

[Guest 2]

Not sure then sorry, maybe a C7 regular could comment.

The A4 seems to function everytime but if the engine is 'off' for too long it asks you to start the engine using the key again.

[aurora7]

There are a whole bunch of "conditions" which can cause the stop/start to deactivate and the car continually monitors this. My local Audi master tech rattled these off to me; unfortunately the only one I can remember apart from the engine temp needing to be warmed up was about the aircon/heating, i.e. if the car has to work to get to the desired temperature then the stop/start won't activate. There were loads of other conditions though, I'll try to remember them/find out what they were.

[ianfarnham]

Loads of conditions have to be satisfied (they're listed in handbook) and include engine temperature , battery charge state, interior cabin air temperature, not on a hill, not turning the steering. I found in warm weather last autumn it stops quite frequently but now in the cold weather you have to have completed quite a long run (eg 25 miles) before it cuts out. i suspect that cabin temperature and state of battery charge are two of the key factors.

[nealeb]

My A6 is certainly a bit variable about start/stop as well, but I've just put it down to the car figuring out what it feels like on the day! Certainly in this cold weather it seems less likely that it will stop compared with the warmer weather we were having.

I'm just pleased that I've found out how to start the engine by just relaxing pressure on the brake pedal; hill assist keeps the brakes on but you can start the engine a second or two earlier as you see the lights start to change or a gap on a roundabout get closer and feel confident that you can go immediately you want.

[KAM]

I'm just pleased that I've found out how to start the engine by just relaxing pressure on the brake pedal

The initial force on the brake pedal also seems to be one of the many factors that influences engine stop. I've found that you can brake the car (mine is an auto so I'm not sure how this translates to manuals) to a gentle standstill and then hold it stationary on the brake pedal without the engine stopping. Press a bit harder however and it will stop. Releasing the pressure on the brake pedal once again restarts the engine but doesn't permit forward movement. The ability to stop with the engine still running is indeed very useful at roundabouts.

I think the conditions that govern engine stop are actually pretty sensible overall. Some are obviously functional (e.g. operating temperature) and some are safety-related (amount of lock, steepness of hill etc). To be honest, I'm not entirely sure what the real purpose of it is. It may benefit mpg, but I suspect the biggest difference will be the amount of CO2 emitted over a given journey.

[ianfarnham]

Yes its a bit like riding a bike, first time it all feels very strange but after 3 months you dont even think about it because you subconsciously adapt driving style (eg brake pedal pressure when you stop) to suit immediate driving need