runs cold

i have a 90 cherokee and it runs about 170 and i think 180 is needed for o2 sensor to kick in. i have a modine radiator that i put in a year ago and i have got a 195 tstat. what could be the problem?

I recently asked a similar question myself. Turns out the O2 sensor (if you have the OEM three wire one) has a built in heater of its own, so it is independent of the coolant temperature. If the built in heater goes bad, it takes longer for the O2 sensor to get hot enough to work properly.

If you have an after market one wire O2 sensor it takes longer for it to get hot and it robs you of fuel mileage. In fact I am not even sure the one wire O2 sensors will even work with a Renix. Probably not.

You ask what could be the problem, but are you really having a problem? Don't trust the temperature gauge on the dash. They are not precise, or terribly accurate. Where are you reading the 170, and are you using a seperate temperature measurement device to verify the temperature?

my readings are from the dash. is there another sensor that the computer runs off of?

Yes. The sensor in the upper head near the rear drivers side, close to the Map sensor is attached the gauge.

There is another sensor on the drivers side of the block hidden up underneath the intake & exhaust manifolds in the engine block that feeds the ECU.