Ok. Ok... ok. So, after the fuel injector swap, my MPG dropped from the typical 15 mpg average to around 12.5/13. I expected this as the PCM has to relearn fuel trim and driving habits...

...but what i didn't expect is how my last tank averaged 13.4 mpg, and my current tank just added up to 17.1 mpg... AND I WAS DRIVING IT HARDER.

I didn't do any different routes, but I was definitely jumping on the gas a bit more, just for fun. I hadn't been hard on it since the swap because i wanted the PCM to relearn my normal driving habits, but then I decided I wanted to play with my improved acceleration...

and I got BETTER gas mileage.

It's probably a fluke... but do you think being harder on the throttle actually helped with the PCM's relearning?

 

HEY! I'm having a similar issue. (ECM though). I'm a extreme "feather footer". I've mentioned in a few posts that I got a fluke high mileage figure actually ON the trip when I picked up the 703's for my 90 Renix. I had a buddy driving! (got 19 on the 300 mi. down , and 18, back) Those trips had been in the 16-17 mpg range). He was a good bit heavier on the pedal, (maybe average?), but also seemed to keep getting in a spot where he needed to punch it.
Was wondering if "parameters" or something were set more for the average driver. Maybe we're not ending up spending enough time at an optimum RPM range, more time creeping up to speed at a lower rpm. BUT, that trip was nearly all Hwy, and going the same sped, 60-65, (he would get to it faster though). Now, after the swap I need to check again.

So three main differences:

*He stayed in the "truck lane". Overtaking a slower vehicle, every time, (instead of just changing lanes ahead of time), he would slow down, sometimes even with breaks, follow slower for just a minute, then dive into the fast lane and pass. Then get back in the truck lane and repeat.

*Was heavier on the gas on the maybe 15% of "rural" driving.

* The humidity was sky high. The Renix w/knock sensor might have given me unusually high spark advance.

Then also there is plain old carbon. Some tanks I might only "put it to task", back up my three mile road twice a week. Putten' around here, giong down, and putten around down there all could be less than optimum for keeping it cleaned out.

Maybe there is such a thing as going too light on the pedal. Maybe I should put tape over the vacuum gauge I installed, crank the tunes, role down the window and let that foot fall down.

 

I too am having the similar issue.
Very good question and theory about driving under a preferred RPM band.
I installed Liberty injectors on my 89 XJ and I too have been driving like a granny trying to get more mpg's. They are suppose to be only 1lb different from stock plus the 4 holes instead of one. I'm getting 13mpg city and 18 hwy. I have 4.10 gears, 31" tires, Auto Trans Aw4 and NP242 Xfer case.

I was actually having this discussion with a guy a couple days ago and he said "that's your problem, your not driving, you're *****footing around." I will change my driving habits and test this theory.

 

I only get 9 mpgs on a good day any suggestions on what to do to help this other than driving lighter?

 

What year is your Cherokee and what mods do you have; tire size, gears, xmission etc?

 

I think opening up the throttle more often definitely helps the computer, but it's also good for any engine thats been around low rpm's a while. It helps clear out any built up gunk in the fuel system which will also affect mpg slightly.

 

I suggest you fill out your profile with your Jeep info or include it in your posts.

 

I agree with your friends. Just drive it.

 

1996
32 inch tires 3.5" lift 355 gears and Borla exhaust with glass packs

 

And sorry I'm new thanks for the advice though

 

Welcome to the 9 mpg club

 

Have you ever recalibrated your speedo for the 32" tires?

 

The slower you accelerate, the longer your engine works to accelerate, which is what is using the most gas. 10 seconds of work then coast, or 2 seconds then coast. Which do you think uses more?

 

Yea I did and yea I understand you on that one

 

I get best mpg in town... I know its odd, about 15mpg in town (I dog my poor XJ) and on the highway I am getting only about 13mpg.... I belive this to be an odd problem. Anyone else seem to have that strange city is better then hwy?


P.s. could it be that my t-case never leaves fulltime?????? I go everywhere in F/T.