ok guys im lost now my xj is getting very ****ty mpg i mean on a half a tank ill go maybe 50 miles what you all think is going on

 

Before someone comes and flames the crap out of you, how about some details?
Year, engine, trans, lift size, tires, other mods... What have you tried? When was your last tuneup?

 

yeah prob should have listed all that 4.0 aw4 auto no lift 31 mts has 204k last tune up was around 200k trans was just rebuilt i ordered the accel super tune up kit from quadratec has new vac lines and air filter seafoamed it has full exhaust with high flow cat put on around 180k also ordered rocket air intake

 

I only get 75 miles on a half tank welcome to the club of Cherokee gas gusslers

 

Oxygen sensor failure is certainly a possiblity. They're only good for about 80,000 miles.

 

Would u recommended I replace mine

 

How many miles have you had your Jeep? They not only fail, they get lazy and unresponsive.

 

My Jeep has 180k and I've put about 5k on it how do u know if it has failed

 

If you see a steady decrease in mileage. Or sometimes you will see your idle slowly roughen up little by little. For the price of an upstream NTK o2 sensor off rockauto.com, that should be one of the first things you do when getting a new jeep. Besides, if it slightly improves your mileage, which it should, it will pay itself off in no time

 

You check and see if you have any bad leaks like your gasket tighten up the valve cover and oil pan check your intake and exhaust manifold bolts see if there is Air getting into your engine . Test by taking brake cleaner and spray different areas and see if idle change at all basically low dollar leak detaction

 

When spraying for vacuum leaks it's probably better to use throttle body cleaner as it is oxygen sensor safe. Some aerosols, if they come in contact with the tip of the oxygen sensor, will damage it.

 

http://www.naxja.org/forum/showthrea...ht=sensor+test

 

Yeah I'm going to try that this weekend and it use to not be this bad but its at the point I don't wanna put gas in it Haha

 

Yes throttle body cleaner better choice haha I cant believe I said that