Isuzu Repair: 94 isuzu rode, honda passport, poor gas mileage, vacuum gauge

Question
I have a 94 Passport with 3.2 L V6 and 4X4. It has 110000 miles on it. I get very poor gas mileage on it (about 220 miles to a tank full). I have changed the upstream O2 sensor and plugs. I have also tried cleaning the throttle plate. Put in a couple of bottles of Seafoam, and it did seem to make the power output a little better. The car runs well and performs good. The only thing I can see that happens is that the temperature shows a little lower, but the heater does work (I am in Iowa.. its COLD). I am thinking about changing the thermostat and temperature sensor. Any suggestions?

Answer
Hello Ron! Well Your temperature should run about 185-195 degrees. Your thermostat could be stuck open or you could have a faulty temperature sending unit. Also check your evap sensor and hook up a vacuum gauge to see if their is any faults in your throttle body or you could do a compression test, wet and dry.