What is the normal operating water temp on a 91 3.1L?
That all depends on the thermostat that is installed. From the
factory it came with a 195 degree thermostat. However there are 180
and 160 degree ones available. Under normal conditions the
operating temp should stay around the temp of the thermostat
installed. Some fluctuation is normal, especially in stop an go
traffic when there is no air flowing through the radiator.