It is on the Intake. It is under the TB. There are two little things that connect there. One that has only one wire, and one with two or three. It is the one with two or three [also the larger one]. Pull that out, replace, clean all connections. You may want to try cleaning all the connections first. What temp are you reading anyways? And just because the needle is only 1/4 passed 100* doesn't mean the car is too cold. And what about the gauge? Do you know if it works? Does it move at all? You try cleaning the connection for the cluster? Just some other stuff it could be.
'89 SSE - GX3 -190k, 155k on body - Back for another ride.