I had a bad upstream o2 sensor so I unplugged it and drove about a month like that with no issues other than occasional pinging....I got way better fuel milage than its ever gotten with it unplugged...I bought a new sensor and after I installed it 3 gallons of fuel last me 15 miles and it idles real rough and dies at stops...if I wasn't worried about the preignition eventually causing low end issues I would unplug it again and just run without it...I have waaaaay more power than I used to when the old one was in it so I'm assuming the new one is either bad or just sending a lean condition to the computer...anyone got any thoughts? 3.9l 4x2

 

What brand sensor did you install? How is the cat?

 

Cat looks to be fine but I did have to couple the pipe back on at the y pipe just after the sensor cause it fell off a few weeks ago...its not leaking or anything so I don't know why that would cause an issue. Its an ISA o2 sensor and from what I can tell thier parts and service have a 4-5 star rating on everything I can find including the BBB.

 

These trucks don't like anything but NTK, or Denso O2 sensors...... They just don't seem to get along well with other brands.

 

Yep,put a NTK or oem 02 in it.
Many sensors on these trucks wont work correctly if they're aftermarket.