99 Purple XJ

I got kind of a newbie question but my O2 sensors would they be bad if im averaging 11.5 mpg as the over head console says and theyre original with 130000 miles on them its a 1999 xj 4.0

VTJeep

it matters to me! thats exactly the gas imlage i was getting before i switched out my o2's. the downstream was bad and had tripped the CEL. as soon as the new ones were in it jumped to like 18 mpg. make sure you get the good quality 4-wire, heated o2's. cheap ones suck. also, it had this bad hesitation and would make this pop, kinda like a backfire, from the manifold. all thats gone now!

99 Purple XJ

Ill give them a shot and one more question will i damage anything if i remove my front driveshaft for daily driving i have a np 242

VTJeep

leading up to my o2's being replaced, i went thru and replaced every other part that could be causing the bad gas milage. plugs, wires, cap, rotor and all fluids are things to consider, too. allowing your engine to run less restriced is a good way to gain a LITTLE fuel economy and HP. uplug the ac compressor, do a DIY intake and run some sea foam thru your engine. litterally pour it into your manifold, slowly, and have a friend there to keep his foot on the gas so the rpm's stay up.

VTJeep

no! you have fixed yokes. just drive it as you would nomally. why you romving it? just curious

99 Purple XJ

Ive done cap rotor plugs wires sea foamed everything already made a DIY intake and put a more free flowing exhaust on

VTJeep

cool, thats the way. i think mine has litterally same set up, forgot to mention the free flowing muffler! haha. another thing to do is to add an aux. radiator for the tranny. right now your engine and tranny are being cooled be the same radiator. separating these two wont make engine run much cooler, but your tranny will thank you.

BeaglesXJ

Im curious too. My overhead console says im getting 12.4 on average. Im thinking I may have a clogged cat or my o2 sensors are bad. Plus the fact that I have a nice little crack in my manifold.

VTJeep

air-fuel-spark! all have to be working properly, and in relation too each other (ie, matched amounts of delivery from each) so yea, having a poss. bad cat, and a craked manifold, etc. would all be contributing factors in your poor mileage.