Coolant sensor that was just replaced

My temp gauge will not register any temp on my ford ranger (2000) 4x4 ssion
servicedss4.0 liter. I have plenty of heat, goodair conditioner, new andplug
wires, plugs, gas filter, all new air filters, new oil change, had transmission
serviced, also had a full diagnostic performed and mechanic said he couldn't
find anything wrong with it but said he did reset it. Now the gauge inside still
won't show any temp.reading. if you don't let it warm up for 15 minutes before
you leave, it will bogg down and doesn't want to change gears like it should.the
temp sensor is brand new and had another mechanic help me install. It seems
to run better or smoother since then but still has that god awlful sathuddering
or shaking. Especially when you simply cruise steady at 45 or even 65. I
noticed when I took qtips and rubbing alcohol and rubbed on the prongs of the
new sensor plugin, that the gauge went up to 180 degrees when it got warm
but stopped the next day. Please can someone give me they're thoughts on
this? Its driving me bonkers. Is the new sensor bad or is it something else?