Very glad to be a first time Mercedes owner. I bought a 1985 380se this past weekend and it is in very good condition, however there are two problems that I need fixed ASAP.First one is that it runs fast while in park or neutral ( about 1600 rpm) but as soon as I shift to reverse or drive, it drops to 600 rpm. After reading many posts here, I replaced the OVP and the idle slide valve. No change. Any suggestions? Also My central locking doesn't work. I know they are controlled by vacuum. They wiggle, but don't operate. Is this related?

Door locks on a 126 chassis are done through a reverse cycle pump. Pressure does one way and vacuum the other. The pump is in the trunk with the spare tire.

The idle control has its own controller those years and often just has bad solder connections on its PC poard. It is obviously not doing its job if the idle is up to 1600 and you have replaced the valve.

Sometimes it could also be because of the accelerator cable being jammed. Lube the links to free it - like it did for my dad's 126, and it worked well.