My coolant temp guage has been going up and down rather quickly lately and my heater didn't work all the time. So I have just changed my thermostat and changed my temp sensor about a week ago. Well, now that I changed my thermostat out, my guage is extremely erratic. Jitters very quickly from the bottom end of the guage to the top end. But if I hit the gas, or drive down the road at high RPM's, it will smooth out, but not all the way.
What the hell did I mess up while I was in there? I couldn't get to one bolt on the thermostat housing so I had to take off the intake manifold to get to it easier, so I'm thinking I may have done something with all the sensors under there.
What feeds the guage its reading that could be messed up. Is there a pigtail with a short in it somewhere? Please help. Thanks.

1992 V6 RS with 182K miles.

 

Check the wire going to the sensor on the driver's side head, under the exhaust manifold, between cylinders 1 and 3. Should be a green wire on there. Maybe it's loose and vibrations are causing it to break the connection?

 

Yes, it's not a very secure connection there. What is that sensor for?

 

The temp gauge.