Hi everybody,
I have a 98 with the 4.0 and the the aw4 trans. Recently I have put on a 3" rough country lift with 31" A/T tires. I mostly drive in town with the occasional highway drive. I know it's an XJ so I by no means expect to get 25+ mpgs, but I feel I should be getting better than 9! I have cleaned the throttle body, IAC, put new injectors, spark plugs, cap and rotor, wires, and checked pretty well for vacuum leaks. I'm running out of ideas, so all input would be appreciated! I'm 17 and have been learning a lot. It's just hard to pay for gas at this rate!!

 

Clean air filter? Better yet would be new. Drive like old man, easy on starts, try to anticapate traffic lights and coast further to stop lights. Proper inflation on tires. Avoid idleing for long periods. Remove junk from trunk.

 

Thanks for the reply,
I forgot to mention that I do have a new air filter, and have been trying to drive "like a grandpa."

Also, there is a strong raw fuel smell behind my jeep. Thanks again!

 

What kind of shape are your O2 sensors in? Any engine codes?

 

Did you flash the ecu after doing injectors or any other mods?

 

No codes, and about 6 months ago I put a new NTK upstream O2 sensor in...forgot about that too...oops. Thanks guys! I have not flashed the ECU, actually not sure what that means? I did touch the cables together and then put them back on, and pull the headlight switch for ten seconds. Thanks again!

 

How is your exhaust manifold? Are there any cracks in it? That will kill gas mileage and cause you to run rich. Usually there are cracks where the downpipe means the manifold.

 

Ok, will check into the exhaust manifold after school! Any special way of doing this? Or just visually looking for cracks?

 

Map sensor could be bad too.

 

Thanks, but I did find a test for it, and it passed. I've been trying things for a while now and forgot about that as well! Appreciate the tip!

 

Clean throttle body and IAC. Check for vacume leaks. Maybe try fuel injector cleaner, someone will probably recomend a brand.

 

is the strong fuel smell coming from the exhaust? or you might have a fuel leak by the tank

 

Definitely coming from exhaust. Tailpipe is pretty black, but oil is always perfectly full when i go to check/change it. Thanks!

 

Fuel injector cleaner definitely wouldn't hurt. I always use BG44K which is a bit spendy compared to others but definitely worth it. I usually run a can through the fuel system every other oil change. Put it in with a full tank, fill up the tank again when you're at about half, then run to empty.

 

Also sorry if I missed it but replace your fuel filter if its been a while and did you properly gap your spark plugs?