1987 300D with cold idle problem
When I bought the car, I could start the engine, and it would idle high for a while, when the engine warmed up, it would idle down to about 700 RPM.

A while ago, I noticed that the engine would not idle high when it started, and I would have to hold my foot on the throttle for a few minutes, or it would die.
I turned up the base idle so that then engine idles just above 400RPM when cold, and about 950 when warm.
I only did that as a work-a-round until I can find the proper fix.

I believe that there is some mechanism that is supposed to raise the RPM when the engine is cold(similar to what a gasser does), but I have not been able to figure out what that might be.

I have suspected a vacuum leak, so I put a smoke detector on it, and cant find any leaks.

I have checked the OVP and didnt find any problem, besides that, the the tach works fine.

Can someone please assist in pointing me in the right direction?
Thanks,