1993 190E 2.3L WON'T START IN MN WINTER!
 

Okay, my car runs great warm. Trying to get it started most days below 40 degrees Ferenheight; it has taken between 10 min, to 24 hours of cranking on my poor starter. We have checked most sensors, and vacuum lines, but I can tell there is something we are missing. We both have been mechanics (my boyfriend more than I), so we know what to look for, for the most part. I guess I am looking for some insight from a person who has history with these lovely Mercedes Benzs. Any help would be greatly appreciated.

Wiring
 

Many of those 93's are plagued with poor engine harness wiring. It was made to be bio degradable, but the green people screwed up. Insulation starts breaking off and wires start shorting out. Have you evaluated the wiring?

Cold start valve or idle control valve....or possibly a temp sensor giving faulty info to the computer.

I went through the same problem 35 and up started fine under 35 would not start! checked everything had it check on a OBD nothing! My wifes uncle Benz Mec said crank sensor or coil it was the coil! Well really one of the two coils in my 400E check the coil for week spark in the cold I bet thats it!

Rocket, try swapping a known good coil for yours and see if that resolves the low temperature starting problem. A new coil will run about $75. Consider having a local MB-trained independent tech troubleshoot the root cause of the problem instead of throwing parts at it.

When I checked for spark on my 400E, the bad coil did not thorw a strong visible spark but the good coil did! Pull the coil wire off the cap and hold it close to the cap connection like a quarter inch away then have someone try to crank it. If you done see a strong spark it the coil!