A Favor

This is for someone that has a manual for a 90 XJ. If you could look up and see if it has some specifications for the coolant sensor for the ECM.

I don't know how it works but I'm guessing its resistance to ground so some ohms figures is what I need so I can test it.

As a quick test; first thing in the morning when the motor hasn't been run for many hours, I compare the ohm reading for the MAT (manifold air temperature sensor) to the Engine temperature sensor (lower left of block). They should have the same resistance at the smae temperature or near enough.

You might want to add this to your bookmarks.
http://gps-spots.com/Tech_Articles/Engine/Basic_Sensors_Diagnostics.htm

Ok cool thanks for the help. Yeah the problem I am getting is it idles too fast. Especially on cold start, and the only way to get it to settle down is to turn off and restart and even then sometimes it doesn't work.