take it back to the tuner and have him/her log everything and rework the tune

 

He charges for that, my local dealership said it would be 85$ to do a full diagnostics to see why I get such poor fuel mileage whether it be a pcm update or out of range sensor, seem worth it?

 

you would be paying $85 for them to overwrite the tune thats on it, then you would have to get it retuned for things like the fans. Seems like a waste imo.

How much does your tuner charge? $100 for a retune? I think that'd be worth it

 

60 for a retune

 

I'd take it back a retune

 

I agree that you should get it retuned, on a dyno preferably. My 2001 runs great and I don`t drive it like the old man I am, I could get better mpg but I don`t like driving like a old fart in a Prius. I get 12 mpg in city 15 highway, I think 10 is a little low.

 

12 isnt that much different than 10, its kind of in the noise of the data for a 200k period

 

I hear ya lol. I was enjoying excessive amounts of alcohol. I have plenty more irrelevant facts if you ever need them...my Z06 got 28.5-29 on cruise 75

 

In all fairness, every other poster in this thread probably knows more than me about this: but if it was doing this when it was stock, I don't get why everyone is so focused on blaming it on the tune. Have you jacked it up and checked the resistance of each wheel? (Wheel hubs/bearings, diffs) maybe wrong diff fluid, alignment out, wheel hubs are known problems. I still lean towards some previous repair being done with the wrong part or maybe wrong torque setting based on the other model. I know some websites have NBS listed as 2000-2006. If you enter vehicle info as 99 its just going to show up as an OBS model. If you don't already do it, put your year in as a 2000.

 

because the tune is exactly what controls how much fuel the engine uses.........

The tune controls when/if the TCC locks up..........

The tune controls where the trans shifts.............

The tune controls the speedo that may or may not be accurate thus throwing off the numbers this guy is calculating.........

Because the tune is more likely to be "less than optimized" vs "a wrong part" installed by the PO or even the OP

Also, since 1988 in the pickups and 1992 in the Suburbans; there are no front locking hubs. Everything up front spins on a 4x4 when disengaged. A wheel hub thats dragging enough to eat MPG is going to be A) noisy B) hot