I have a 4.0, automatic trans, very mild 31 X 10.50's A/T, and a 3.5" lift, I'm only getting 10 MPG, any tips on brands for Spark Plugs/wires/cap + rotor/etc... also other helpful suggestions

 

Anything new should help.

MPG's depend a lot on how you drive, I get 14 MPG with 31's and a 4.5 inch lift. I try to not let my RPMs get over 2000

 

yes... new is good, but quality is a big factor, too. i bought a NEW TPS offline and it worked, but it worked badly and was reading no more than 2-3% of throttle, even if on it 100%... so new was all well and good, but that didnt stop it from sucking...
anyways... things to replace for a tune up:
-starting at battery, are all terminals and wires (both power and ground) clean and well connected
-new plugs/wires
-new cap/rotor
-new air filter
-new TPS
-new IAC valve
-new CPS (94 and earlier)
-new o2's
other than that, doing things like sea foam can help to remove some of the build up of carbon and other swag ya dont want in there. sea foam can be added to oil, gas or directly into manifold.
ALSO! dont forget to check all fluids! good oil, coolant and diff oil are very important. replacing all of this stuff is pricey, i think i did everything on this list (save the CPS...) to mine in the year that ive owned it. also did a new battery and fuel pump recently. and i still need to do the PCM. and at over 300 dollars (i dont skimp on quality) im balking a little. course, i just dropped like 600 at quadratec doing random things like new leafs, shocks and some other stuff, instead of replacing PCM... but i am still trying to determine if it really is the PCM... joy...
ok, remember to start small and simple and get it on a code reader before diving and droppin some cash!! good luck!!

 

The biggest imporvements Ive had aside from typical tune up items is a thorough cleaning of the throttle body/IAC/entire intake and a new O2 sensor. Then things like ditching the mechanical fan, opening up the exhaust and CIA helps alot too.

I get 16-18 on 4.5" and 33's, then again i dont have a slushbox

 

I get 11 and I'm happy

Brandon

 

I get 11 and I'm happy

Brandon

Oh but try a new o2 sencer.

 

Well, I have a 96 HO automatic, 2'' BB, spacers and shackles. Pretty sure the gears are a 3.73. I did the simple 10 gallons of gas set the tripometer. 160 miles to the 10 gallons of gas. 16MPG. I run 235/75/15 on stock 10 hole style wheels. Going to a soft 8 next week in a 15x8 configuration with a 3.75 BS, curious if any change.

 

Dont forget that if you have a roof rack that you can lose MPGs also the xj is designed like a cinder block theyre not very arodynamic

 

gettin 16mpg on a 6.5 lift on 33 12.50 15's at 20 psi, was gettin about 12, then i changed my intake to the 2000 xj one, and the injectors to the dodge neon 703's, and relocated the iac sensor to the air box, and now i'm gettin 16mpg

 

 

How does the 2000 intake improve mileage?

 

it has longer equal length runners so it allows the engine to breath better at higher RPM's, not so great for low rpms. Staying in the engines power band is much better for MPG than bogging the motor down. The engine uses alot of fuel when its bogged down

 

Also in the winter months your mpg will tend to drop from the cooler air. If your cooling system is in good shape, you could try a warm air intake.

 

im on stock axles lifted up there on 35s........
Was getting 8 mpg.... Changed out my rotor. dist. Spark plugs (the basic ones from autozone are what basically comes stock with your jeep and they work excellent) replaced my upstream o2 spark plug wires.......and now im getting 12-13 FTW ON 35s!

 

sry "iat" sensor, intake air temp sensor