Just wanted to add my information to the database here. I had been having a cold start problem with my 1988 190 2.3. Every morning it was hard to start but the rest of the day it would start ok. It turned out that it was in fact the coolant temperature sensor that had gone bad. This is a great site thanks.

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1996 E320
2000 C230 Kompressor
1988 190e 2.3 - 225K miles, owned for 7 years. I cannot say enough good things about this car. Very well built, even at 225 it ran like new.