I have a 1986 190d mercedes every time rains or the car is washed it runs really ruff and wants to stall at stops. I tried an experiment and wash the front end of the car and had no problems. I then washed the back end and it acted up again. When it does act up the ac does not want to work until it is not running ruff. We also tried taping the fuel door and it was not as bad. This has been going on for a while and has been to a mercedes shop but to no avail.