Which one? Need help
 

1992 300E difficult cold start and idle stumbles for a bit after start. Checked the cold start valve by putting power to it and it clicks, so assume the CSV is functioning. There are 3 sensors on the rear half of the head. The 4 pin in the rear, 1 pin in the middle and a 2 pin closes to the front. The 1 pin is for the temperature gauge I believe. Which sensor controls the CSV function the 4 or 2 pin? Anything else I should check? Thanks for any and all input.