I was wondering if a previous owner had changed out the ECU. I have a rebuilt set of injectors sized for the 94 3.9 about 2 or so years old. The O2 Sensor is 3 years old. I'm getting around 14-15 mpg's. When I did the plenum before I changed the injectors I got 19 mpg's on that first tank of gas which was mostly hwy miles. Then it started going downhill and has stabilized at 14-15.

 

Being I know your good at preventative maintenance, I wont state the obvious.

but, often times people neglect the cat. You have inspections iirc. How old is the converter?

I do however forget what your truck is: v8 or v6 2 or 4 wheel?

 

CAT is about 2 years old its a 3.9 2wd

 

OK Tires were low, down to <30PSI which is odd since they have less than 7500 miles on them new. Edit-I used my tool to tighten the stems. I detected no looseness.
What brand O2 Sensor is meant for the 94 3.9?

 

Bosch.

 

Really? Were those stock equipment? I know some of the newer trucks really dislike the bosch sensors.....

 

nope. Dodges don't seem to like the Bosch sensors at least not for very long. Look for NTK, that was OE.

 

mine has been doing great for 40k+ miles.

 

Lucky.

 

X2.... I usually get a year if I am lucky out of a Bosch branded O2.