I am lookind at two different things (look like sensors to me). They screw into the front of the TPI manifold and they both appear to screw into the coolant passages. One is really big (15/16" I believe) and the other one is substantially smaller (19mm). I am almost 100% sure that the smaller one is the coolant temperature sensor. What is the other one? Any help would be greatly appreciated. Oh yeah, this is in an '86 manifold. Thanks guys!

 

The "larger one" is for your cold start injector.

 

I guess I should have been a little more specific. These sensors (potentially) screw into the manifold right underneath the thermostat housing area.

 

One is for the cold start injector as stated. The other it the coolant sensor for the ECM.