@Droz,
Forget my question about pitot. I checked the command in the game and yes, pitot is simulated. Moreover, I read some document on internet to understand the purpose of pitot system. And yes, it is simulated in the game, I saw a video on youtube of a guy making a good example in a BF110 : he flight in a cloud, every windows gets freezed and he check the indicated speed with and without the pitot heater activated. This make a great difference in indicated speed.
So, now that I understand pitot, tell me if I am wrong but I don't think it can help to avoid motor to cut out but I did a try. There is not difference. With or without pitot, the motor cut out.
So, so far, I still don't know how to avoid the motor to sputter and cut out in clouds.
Thanks you very much Droz, the pitot do not solve the problem but I understand what is a pitot and when we must use it.
@Ivank, thank you for the information. Any idea of how to manage the problem to avoid sputter ?
EDIT : here is the video I was talking about above :