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mileage tips

XgeekstarX

NAXJA Forum User
i'm getting maybe 13mpg (240-250 miles on a full tank) in my stock xj. with gas like it is i can't handle it anymore. i need to get an alignment and i'm going to get a new oxygen sensor in hopes of getting a little better mileage. anyone know a ballpark of how much this will actually boost my mpg? any other tips to get better mileage would help a lot. thanks guys.

edit:
92 4.0L HO
aw4
123,000 miles
3.55 gears
 
Last edited:
XgeekstarX said:
i'm getting maybe 13mpg (240-250 miles on a full tank) in my stock xj. with gas like it is i can't handle it anymore. i need to get an alignment and i'm going to get a new oxygen sensor in hopes of getting a little better mileage. anyone know a ballpark of how much this will actually boost my mpg? any other tips to get better mileage would help a lot. thanks guys.

edit:
92 4.0L HO
aw4
123,000 miles
3.55 gears
ummm lets see:
- dump the roof rack (even stock one)
- get good set of street tires
- clean air filter or get new air filter element (maybe improve air intake by getting cold air)
- cap/rotor/plugs/wires
- clean the tb
- wash it and wax it so that it cuts through air better
- search oem for more :D
 
i had lost a lot of power and a good bit of economy in my '93 manual 177k.
i went through a lot of stuff, and increased both appreciably. some things may be irrelevant, dunno. i would;
check codes
test/replace the o2 sens
make sure you have a nice clean air filter
test vacuum
test map, cts and iat sensors, replace any that are faulty
clean tps
seafoam or other boogie juice of your choice for your fuel system
figure out if you have a clogged cat

search and search and search
 
i've already put new cap/wires/plugs on it hoping it would help out, but nothing. i seafoamed it around the same time and cleaned out the throttle body.

i just know some of the guys on here say they get around 20mpg and it makes me jealous. =(
 
XgeekstarX said:
i've already put new cap/wires/plugs on it hoping it would help out, but nothing. i seafoamed it around the same time and cleaned out the throttle body.

i just know some of the guys on here say they get around 20mpg and it makes me jealous. =(
Do you have a lead foot? What plugs are you running? what wires? Some have best performance with oem plugs.
 
My Renix was getting really bad mileage. I was chipping away at the problem a little at a time and making gains. Tune up, O2, tire pressure etc.
I finally hit what seems to be the magic solution, for me.
I changed all the connecting rod bearings and drove it like it was new (break in period), really easy on the gas, rarely over 1500 (2000) RPM´s. At the same time I scrubbed out, all the seldom seen connectors (engine temp. O2 and on my Renix the knock sensor) with contact spray and a very small brush. One or the other or a combination of both, but whatever, my mileage went way up (like 20%).
 
I thought I had read somewhere on this forum that swapping out the injectors to smaller Ford injectors will help lots with mileage... I know there's a list of compatible Ford and Chevy injectors... uh, it's here:
http://www.arizonaxj.com/tech/InjectorInfo.html
I'd like to hear from someone who's done an injector swap to get better mileage.
regards,
jlex.
 
Do a search on Ford Injectors. Apparently, everyone raves about the 19 lb. Ford injectors. They supposedly have a better spray pattern (4 holes instead of one) so they're more efficient. Deals can be had on Ebay. In a higher mileage jeep like yours, I'll bet they're the solution you're looking for.
jlex.
 
I did the change to the Ford injectors. My 88 was going on 180k and it didn't look like they had even been replaced or even checked. Two where leaking on the outside very slightly and after shutting off the engine popping the hood and checking for fuel pressure I was getting but a dribble from the fuel rail, so I suspect one was leaking internally. My Oil always smelled like gas.
Now I have none of these symptoms, plus the Fords were cheaper to get.
I can't tell you if it because they were a newer design or if the spray pattern was better or if that had anything to do with it but my mileage went from around 14 to just about 17.5 MPG the next tank full.
Best I could tell you is if you have the orignals and you have the time and the cash to get them checked you might want to do it.
I didn't have the time to get mine checked so I did swaptronics on the lot of them, it just happen to work for me.
 
With a better spray pattern I don't know how much it would help, but there was a thread about adding Acetone to the gas. 1fl.oz. / 5gal gas. It helped a lot with part-throttle response in mine - but I have a lead foot, so I only get around 13-15MPG, depending how many people I find to race :)

O2 sensors are supposed to be good for 100K+ miles, and I think they either work or they don't, no in-between - could be wrong.

Do a search for a "hyper ground kit" on google. My friend showed me one (I think it's called "hyper ground", again, not sure) - it basically upgrades the grounds for better performance by everything. The web site said 13HP and several MPG on a stock Evo 8 - my friend said he heard about them from somebody who never would have believed the improvement he got until he felt it himself, as did my friend, who said the same. The next $100+ disposable income I get goes to one of the generic kits they have.

Also you may want to replace all your wires with higher-guage (less resistance - same principle as the ground kit). 5-90 makes them, so does some guy [email protected] - could be the same guy, I think they're both in San Jose, CA.

My Jeep is a screamer from 3k-redline, still has some nut down low, but low-restriction intake and exhaust (Borla cat-back and drilled out the honeycomb from my Cat :), and home-made K&N) and a shorter-than-stock intake really doesn't help low-end too much, which is where you are when driving, which means that's how you get your good mileage. You can get aTB spacer to help lengthen the intake and bring the torque band down a little.

You can manually shift the tranny. Jeeps stay in higher gears when lower gears would be MUCH more suited to the conditions, ie, climbing a hill @40MPH in 4th, when the same throttle position on the same hill in 2nd would have you going 55MPH. This could be due to my mods too, and the computer not knowing how much more torque it would have if it would downshift.

Upgrade the ignition with MSD/comparable unit, high-voltage coil, etc. Dunno how easy it would be to swap a coil-on-plug from 00+ 4.0 into yours. Probably not easy.

If you changed your t-stat to something other than stock (195*F), change back to stock. Less coolant circulating = less parasitic loss.

Run synthetics in everything but your AW4 - I hear they don't like synthetics or additives too much.

Ummm........yeah........stay with 87 octane/regular unleaded unless your motor knocks......scrape your battery terminals clean, and the connectors......the oxidation I heard is the same color as the lead, so just give them a good wire brushing.

Sorry, I didn't expect to say so much :)
 
So let me ask a question then:

I have a 94ZJ and a 95XJ, if I am reading the chart right in the link provided I have 21# injectors and 39psi fuel rail...SO...does this mean that if I put in the 19# ford injectors my fuel mileage will raise slightly due to the improved pattern and the lower consumption and if so would this adversly effect my motor in any way?

If all looks copasetic and I do this, what will the computer think? will I have to do any other mods to make it work?

Thanks,

JC95
 
jeepcherokee95 said:
So let me ask a question then:

I have a 94ZJ and a 95XJ, if I am reading the chart right in the link provided I have 21# injectors and 39psi fuel rail...SO...does this mean that if I put in the 19# ford injectors my fuel mileage will raise slightly due to the improved pattern and the lower consumption and if so would this adversly effect my motor in any way?

If all looks copasetic and I do this, what will the computer think? will I have to do any other mods to make it work?

Thanks,

JC95

i did a ton of research and some guys are saying that with the HO the 19# injectors will make the engine knock or run lean. the only other option are the ford 22# injectors which defeats my whole purpose of installing them for better fuel mileage.

i'm thinking if i got the 22# injectors that after a while the computer would compensate, but i don't want to spend $200 to find out.
 
I did the swap from stock XJ injectors to 19 lbs Mustang I had for spares.
It solved many problems, from leaking o-rings in the old stuff, to incorrect spray patterns.
I am pretty sure that the ones I took out had been already removed and replaced before.. I found two that did not even match the rest in color-shape. I did this originally trying to cut down on the gas smell inside the cabin, which was solved immediately. Added benefits were a better response at the red light, even acceleration and less effort to get to highway speed, and a jump from 15 mpg to 18 average.
This was all in my dads 89 with auto..
I have seen no adverse effects, and all this was done 11 months ago, with no reoccurrence of leaky injectors.

Angel
 
I have an 89 XJ 4.0 with 129,000 mi. I used to get abou 15 to 17 mpg highway with a 35 mile commute to work. Recently I put in a new fuel pump, fuel filter, oxygen sensor, new EGR sensors, and had all of my injectors cleaned and flow tested. Came to find out that 3 of the 6 injectors needed rebuilding. Had the 3 rebuilt and then did a full tune up. I am now getting gas milage in the neightborhood of 20 to 21.5 mpg. Typically thought i average about 20 mpg. Other than the above mentioned parts replaced/fixed I have started driving no faster than 65 mph, and no longer run my a/c only the vent if I need some cool air. One last thing and I dont know how true it is or not. My mechanic claims that Chevron has the best gas you can buy additive wise for keeping injectors in good shape. Me personally I only run Chevron fuels and once a month or so I run a full tank of Chevron super unleaded vs. regular 82 or so octane. Good luck getting the mpg up!
 
Chevron with Techron always lights up the check engine light on my wife's 98 camaro, so as a rule, I avoid it. Don't really know about performance, but that light is annoying even if the gas is good. I assume it is bad, but it is possible that it is just different and the computer doesn't like different.
 
re: speed. I hooked up with some fast traffic and ran near 85 through most of a tank of gas last week. Guess what? Best gas milage ever..at 20.5
(96 4L Auto 180k mi)
 
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