Lifted 1990 renix, horrible mileage.
 

Ok so to start off, I am a competent mechanic. I am a heavy equipment mechanic/ fabricator by trade. I have built everything on this cherokee my self. Well lets start, 4.88 gears, 35 inch mtr's and 8.5 mpg. It got better mileage before the regear. I have replaced everything under hood to no avail, new exhaust system to. I have checked for closed loop, and yes it is going into closed loop. So basically, at the half tank mark I have went 77 miles:brickwall:
I have checked my mileage to a t with gps. Wth gives. I could of built a late 60's bronco with a small block, and get better mileage, and have a/c.:sick:

your driving a lifted box on 35in tires, and 4.88 gears, your gas mileage is pretty much where i would expect it to be. what kind of driving is it, is it city or highway/country roads?

7.7~ does sound way low even for a lifted jeep. not sure why though

Mostly around town and to the trails. I was getting 16.8 with 3.55 gears, and 33's before I bumped up. I literally put 20 bucks in run a few errands and its gone. And it runs like a top. Passes ca emissions also. If this is the mileage I'm going to get, its time for a ls1. But it should do better than that. Atleast 12 around town I would hope.

well i see you have a stroker, the stroker and 4.88s is a combo for bad gas mileage

manual or auto matic?

It is a auto. Ya the stroker was in with 3.55's and 33's. As a matter of fact i had 35's on for a few months before I regeared. It should do better than this. Its like driving a semi. Hell my 26000 pound mechanics truck does better. lol.

'eh that's what all of my Jeeps have gotten. I am suprised that mine is so bad. 35's with 4.56 gears. Wasted 35 bucks in gas in about 80 miles haha. My F-150 Supercrew gets almost double the MPG any of my Jeeps have got.

what kind of injectors are in there? pools of gas in the runners? are they stuck open? fpr has vacuum? cat plugged? dunno. that really sucks with the mileage. does it feel like it has enough power compared to before the stroke? maybe its a transmission issue...

have you thought about the torque converter of transmission work?

Chrysler gas gauges suck, I know mine jumps all over the place, fill it up all the way drive 100 miles then fill it back up so you know exactly how much gas you used

you should be getting better than that. friend of mine has a very similar set up to yours, 35s, 4.88s, stroker, and a whole bunch of added weight from armor and such. setting the cruise at 70 he pulls around 14 mpg while fully loaded, which is better mpg than he got with the stock motor, 4.88s, and 33s.

my guess is something else is making you run rich. either that or your fuel gauge is off. when did you last replaced your oxygen sensor?

i go round trip to work 55 mi takes 16$ in my f250 diesel, i put 20 in the other day and was lower then when i started , in the jeep, 35's and such,

Message me if you figure out your problem, please. I get the same you get and I have a smaller lift and smaller tires.

put 38s on it 35s to small for 488s lmop

I got 4.10's ax15 and 35's and love it for street and play... I never use 4hi though...

Injectors, are stock. I am going to check those this weekend. Fpr is from stroked jeeps. O2 sensor is brand new, and it is going into closed loop. Transmission is shifting fine, and locking up. Injectors are the only thing left to check, that I can think of.

Sounds like u dont have a problem at all to me... U may have a junk injecter but chances are it woukd spit and studder and run like crap...

Jeeps were never built for gas milage... Well until like 2008 lol

have you put a gauge on the rail yet? you have to set those regulators up with a gauge. it is the adjustable one right? then you should buy the map tweeker too...

im running 38s on 410s im getting around 15 no complaints here but being stick shift makes a big difference and in running ac 24/7 . 703 injectors seem to pick it up a little

703's and AC as well...

yes i dont lead foot either helps alot

35s are pigs...driving a lifted xj is like throwing a brick through the wind...

Fpr was turned up 3 pounds at the rail. This is what my engine builder said has always worked for him.

Uh... So u got a aftermarket pump or what? Cause u cant just "turn up" fuel pressure... Even if u did the regulator would fix that problem...

Yeah something isn't right. Even for a stroker, it should be getting more than 8mpg!
I'm running 3.07's on 32's 5th is almost useless on Freeway, and I average
15mpg. Thing is a dog.
Op with that newer motor, and proper tuning, you should be getting better
mileage.

Yes aftermarket walbro pump.

Yeah but hes running a higher rpm then you on the highway... Drinks more gas... Thats why 4.10 for him puts him back at almost stock power and gas milage... Right now hes got more power (from rpms) and less fuel milage... And u got less power and more gas milage... Well more then him... Your so fad behind in lack of power your gas sucks when excelerating...

3.55 and 33's with a 5 speed was about right for me... Back to stock power and almost stock speedo settings...

89 RENIX (stock 155k poorly maintained), AW4/3.55s/32x11.50 A/T here and I average about 14mpg around town, 16ish on the highway if I keep it under 65.......FWIW.

Woah woah. I have a 2000 XJ, with a cowl intake, and flowmaster exhaust, 3" lift with 31s...and I only get 12 mpg

This isn't fair

Correct, I burn alot of fuel getting up to speed.
Which is why I want to gear up.
Op could gear back down, but 8mpg is bad as bad can be.
Off-highway he isn't seeing 4grand anyway.
Unless he's got the hammer down all day long. :thumbup:

If im seeing 3 grand then he gotta be seeing close to 4 from 70-80... Hes also stroked so I doubt hes been put putting around...

3,000 ouch im around 2100 at 70 if my brain remembers maybe a little less

I was wrong its under 2,000 my spedos about 5 to 8 mphs off also

88 mj, 32's 4.0, auto, 3.55's, 4.5 inch lift New exhaust( header back), 703's, new o2, new fuel pressure regulator..... An I get 10 on highway.

if i were you, i would turn that pressure back down. the factory injectors are just wimpy single hole dealies. maybe you're not getting good atomization...are they rebuilt injectors? an upgraded injector set is a worthwhile investment on a renix. i'm positive my ford yellows helped my mileage after my lift and tires...although its not something i monitor closely, i'm usually getting just over 300 miles to a tank when commuting. that would put me a little under 15mpg. good luck

if the pressure regulator is stock then u can run 100psi and it wont matter... high pressure pump wont do nothin...

Yep, bout an V8 Silverado just so I could get decent gas mileage. ;)

high FLOW lol. he has an adjustable fpr and a higher gpm pump on stock injectors.

The injectors are stock, need to pull them and take a look this weekend. Im sure they are out of there duty cycle. Gonna probably give the 703's a try.