I have a 96 4x4 w/ about 158,000 miles on the engine. As far as i know the O2 sensors on the engine haven't ever been replaced. I'm getting about 12-14 mpg, if i swapped those out for new ones could i expect some good mileage/performance gains?

 

Depends. It is likely that with that many miles and if the sensors are originals, they are probably getting quite lazy. You really have to get a look at the O2 sensor trace and the IPW modifications that the PCM is making to really tell how fast/slow they react. Lazy O2 sensors will definitely reduce fuel economy.

 

I'm pretty good with cars and stuff, but i have no clue what you just said lol. Are you talking about getting a readout of the PCM???

 

Yes. To really know if the sensors are getting lazy, you have to take a look at them with a scanner capable of seeing the IPW and the O2 sensor mV output.

 

Is that something I would have to take it to a shop for??? Or would a handheld scanner tell me that?

 

Depends on what scanner you have.