Well, I was curious if a new 02 sensor would improve mpg any. I was getting about 13 mpg. I replaced the plenum with the hughes kit and went ahead and got an ntk sensor from hughes. The plenum was apparently barely leaking. The original (150k miles) 02 sensor looked good, not sooty at all. I went ahead and replaced it. Mileage did not change. The truck did start to ping occassionally. I drove for about 500 miles and then switched back to the original 02 sensor. Have not heard the truck ping since. Mileage stayed about 13 mpg with both sensors, before and after the new plenum. So, long story, but I personally would not recommend changing the 02 sensor as part of a maintenance schedule, unless you have other driveability issues, cel's, etc. I think you're supposed to change them every 60 or 80k or something like that, but, meh, save that money fo gas, boys! Hopefully someone will find this useful. Individual results may vary. Jswain and jswain incorporated are in no way responsible for mileage lost due to heeding the information contained in this post.
Oh yeah, anybody want to buy an ntk sensor slightly used? Heh heh.

 

I wander if hughes would send you a replacement sensor? Sounds like yours is deffinately faulty.

 

The problem is, most likely, that you did not reset your PCM after changing your sensor. The PCM is used to the results from the old sensor, and its not interpreting the new sensor's results quite correctly yet.

Its also possible that you got a bad sensor, but NTK (NGK) are really good sensors usually. A lot better than Bosch.

The fastest way to make it relearn the sensor(s), or reset the PCM: disconnect battery, turn on headlights for approximately 30 seconds. Turn off headlights, reconnect battery.

 

Yeah, did reset pcm. Reset it when I put the old sensor back in too and it hasn't pinged once with the old sensor back in. Apparently the new sensor makes it run a bit leaner. But I get about the same mileage either way. So, I'm liking the old sensor.

 

Nah, non returnable after taken out of the plastic packaging. Says it on the box, I think.

 

I would contact NTK/NGK then. I can't remember how long exactly, but I know they come with some sort of warranty. Ask them where to send your receipt and whatever paperwork they want to prove that you purchased it and that its defective, and they'll either send you a refund or (more likely) send you a replacement part.

Here you go: http://www.ngksparkplugs.com/About_nGK/contactus.asp

 

My first post here:
Do you know what your fuel trims were before you reset the PCM? Perhaps in resetting the fuel trims (which may or may not have been +%), you may have inserted a learning curve of several drive cycles in order to get the fuel trims back to where they should be based on the current running condition of the engine. Did you reset the PCM again after replacing the new sensor? If not, the PCM may have been making progress to better fuel trim figures right before you reinstalled the old sensor.

Also, unless the sensor is badly worn (very slow cross-counts; bad heater), you shouldn't expect much of a gain in fuel economy or drivability.

 

No idea on the fuel trim. I only know it got the same fuel mileage on bot sensors, but with the new sensor in the engine pinged under heavy acceleration. With the old sensor back in, it does not. I reset pcm each time I changed the sensor, and I put about 500 miles on the new sensor hoping the ping would go away. I guess my point is that if the 02 sensor aint broke, don't fix it. I've heard they need to be replaced at certain mileage intervals, but I'm thinking that may be a myth started by sensor manufacturers. Lol. Basically, I saw no benefit to changing the 150k mile sensor for a new one. Just my experience, but folks are free to change them as often as they like. Unless my experience was an anomoly, seems like a waste of money to put a new 02 in at a specified mileage interval.