13-15 mpg...suggestions

okay, the xj has 193,000 on motor, rebuilt AW4.

1.5 lift
cone filter
dynomax muffler still have cat
lt1 injectors
new O2
new stock cooper plugs

I just took a trip with the truck and averaged 15.5 mpg all highway. WTF? Truck runs great but i know it has better mileage in it. I switch back to the stock injectors a while back and the truck ran like crap and got same if not worse mileage compared to the lt1 injectors so I know its not them. I have ran an intake cleaner through the intake (like seafoam but pressurized sprayed into the TB). It cleans the intake runners and valves. I don't know what else to try. I get 13.5 driving in the city and 15.5 on the express way. The tires are stock size and gears are stock. I now its a 4x4 but I know this truck can do better. No Check Engine light and the bulb works. Suggestions?

I never floor it...its not worth it. I cruise on the express way at like 70-75. truck runs smooth, but I can try a fuel filter...but a clog would cause bogging

what kind of oil are you using?

any brakes hanging up?

75mph is fast for an XJ. All else equal - I bet you would get 18-19 mpg if you cruised at 60-65.

Are all of your wheel bearings in good shape?

how are your ignition wires? cap and rotor?

check for a vacuum leak.

you need to check for anything that would cause your engine not to run perfectly and/or cause increased rolling resistance of the jeep.

HTH

CaptTrev

running mobil 1

speed limit is 70...

no noise while driving or coasting like bad wheel bearings

I replaced the plate in the distributor when i first got the truck and the cap and rotor looked okay...and it runs good!

how bout a bad 02 sensor. My 94 with 31's and stock gears gets 13.5 city and 16.5 highway with new 02, exhaust, and complete tune up.

I think I am going to try a new air temp sensor next.

I have replaced the O2, wondering if I have an exhust leak that is hindering a the o2 reading...

you just gota remember its a JEEP not a sports car.:thumbup:

I wish I got 15 MPG :-(

maybe2fast said:

I have replaced the O2, wondering if I have an exhust leak that is hindering a the o2 reading...

Click to expand...

my pops truck(90 mj) was burning fuel and also failing smog... new o2, and exhaust manifold and its running great) it had a horrible exhaust leak....



btw, NOBODY mentioned tire pressure!
check that too

I think the exhaust manifold or gasket has a leak and it is sucking fresh air

air pressure is a good note, every 3psi you are low, i think its like 1 mpg loss.