- Jul 1, 2013
- 749
My 04 4.2 Envoy recently started getting worse gas mileage, the weird thing is it happened after I got my PCMofNC tune! It was getting about 17-17.5 highway and 15-16 with my mix of city and 2 lane driving (I live in a rural area) before the tune and the mods I did along with it. Now I'm getting consistently around 14 MPG! don't know what the highway mileage is now, haven't had it on a trip since I noticed the gas mileage getting worse. I'm NOT leadfooting either, I'm driving more conservatively after the tune than I did before since the main reason I got it was for mileage.
The mods I have done are: K&N intake, AIR system delete, and catalytic converter delete. Had the pcm tuned as such with shift firmness 1 and no towing, tuned for 87 octane.
I have a shiny clean TB that I could eat off of, new Delco 41-103s, and the K&N isn't dirty. Also has a new fuel filter. Have yet to do the trans. fluid, but I am coming up on that time in about 1000 more miles. Torque converter and transmission seem to be functioning perfectly. The vehicle had a new Tstat a little over a year ago, it was stuck open. Operates at 210 all of the time. Ran Lucas injector cleaner through it with no results.
I really gotta get my MPGs back up, I know losing a mile or two per gallon seems trivial, but gas is killing me! The O2 sensor hasn't been changed, thinking this could be an issue? Also have noticed a whistling sound a lot like a vacuum leak coming from under the hood, but only when I let off the fuel when at road speed do I hear it. Was wondering what that might be as well.
Thanks in advance for any help, it is appreciated!
The mods I have done are: K&N intake, AIR system delete, and catalytic converter delete. Had the pcm tuned as such with shift firmness 1 and no towing, tuned for 87 octane.
I have a shiny clean TB that I could eat off of, new Delco 41-103s, and the K&N isn't dirty. Also has a new fuel filter. Have yet to do the trans. fluid, but I am coming up on that time in about 1000 more miles. Torque converter and transmission seem to be functioning perfectly. The vehicle had a new Tstat a little over a year ago, it was stuck open. Operates at 210 all of the time. Ran Lucas injector cleaner through it with no results.
I really gotta get my MPGs back up, I know losing a mile or two per gallon seems trivial, but gas is killing me! The O2 sensor hasn't been changed, thinking this could be an issue? Also have noticed a whistling sound a lot like a vacuum leak coming from under the hood, but only when I let off the fuel when at road speed do I hear it. Was wondering what that might be as well.
Thanks in advance for any help, it is appreciated!