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.
Bosch Master, ASE Master, L1
33 years MB technician