Low idle when warm

Could anyone please help point me in the right direction?
I have a 1993 190E 2.3L, and have been having intermittent low idle (400 - 500 rpm)for a while, and have been tracking the occurrences more carefully. (This is related to my post earlier in the year about the "Weird Idle involving Overvoltage Relay")

This low idle condition occurs when the engine is hot (>95C). I reach this low idle much sooner in warm weather (being in Vancouver, that is around 20C and sunny)than in cold weather (10 - 15C, rainy and cloudy, of course), presumably since warm weather does not allow the engie to cool as much as I drive.

After low idle in the city, a highway run seems to cool the engine back to 85C, and the car idles normally (800 to 900 rpm) for another short drive. As I sit in traffic again, the engine warms up to between 95C and 110C, and low idle begins again.

I have stalled twice in one day after particularly warm weather, and a long day of city driving. I removed the fuse on the overvoltage relay to "limp" home without letting my engine cool down. The engine idled at 800 - 900 ( I thought that without the OVR, the idle should be higher since no fuel corrections were performed without the OVR) I replaced the fuse at home, and have not stalled again, although the low idle occurs)

I noticed another post about an air slider in another model of Mercedes, but am not sure if my model has an equivalent or where to look for it.

My specific question is "What sensors/controls are involved in idle speed and air intake/supply at the higher engine temperatures?" Is it a defective thermometer that is causing this, or something else?

Thanks in advance for any replies & suggestions.