i have a 91 da b18a1 completely rebuilt to stock specs. the car warms up and idles fine but after driving for about 10 minutes the temp gauge will shoot all the way hot and stick there. if i tap the dash above the gauge it drops back down to normal temp. i switched all the gauges out of my 92 da and they worked fine in that car. at the same time as this happens with the temp gauge my motor will idle up 100-200 rpm and then drop back down no matter what rpm the motor is at. i dont get a check engine light or any codes off the ecu. i would rather not take it to the shop im sure its an easy fix i just can figure out what could be wrong.

 

check your ect sensor and your coolant sending sensor i think thats what its called its the two sensors under your distributor

 

ok thank you. at first i thought it was my iac but i switched it out and still have problems

 

if your facing your car when the distributor is on the left the sensor closest to you the small one is the sending unit and the bigger one behind it is the electronic coolant temperature sensor (ect)

 

wow. this has been a mystery to me for months. explains the tiny bit of coolant on the tranny...