i have a 2000 xj with the coil pack and im getting really bad gas mileage. heres some questions and info on my jeep. Now first of before i post this i know, understand, and respect the law of having a catalytic converter. However when i bought my jeep the P.O cut the cat out and ran straight pipe to a flowmaster and it dumps out the side. The 02 sensor is right after the muffler and is now hooked up. The wires were too short so i had to make them longer by cutting them and adding butt connecters with more wire to be able to plug in the sensor. thats the deal with that. i can smell my jeep running rich and my idle is constantly fluctuating. Sometimes when i try to start it she cranks and cranks so i have to prime the key. I have no low end power in my jeep and im only running 31's with stock gears. something is wrong i tried seafoam and took apart my throtlle body and cleaned it along with all of my sensors. i replaced my air filter with a diy cold air intake and fabbed up a heat shield with the stock air box. Also my tank has problems with building up pressure it takes years to add gas in my tank cuz the gas fills up then goes down and when i first take off my cap a big whoosh of air shoots out? Is this realted with my mpg?

 

i would have to guess that it is more than likely your tank issue, im pretty sure that there is a vent line there some where, id say find it pull it and replace it, also could be a clogged filter or bad fuel pressure regulator or the lines could be clogged those are my guesses

 

i think its something to do with pressure build up, how do i check it? and where is my fuel pressure regualtaor on a 2000 cherokee? Also 2000 xjs the fuel filter is in the tank.. ...damn Jeep

 

your regulator should be on the end of your fuel rail on the front side of the engine its about the size of half of a 35mm film canister

 

How do I know if its bad?

 

with a fuel pressure tester on the top of the rail there should be a valve like a tire stem disconnect the injectors elec hook up and put the tester on that valve and have someone turn the key im not sure what the specs are for it but im sure google could tell you, mine was leaking so thats how i knew to replace it sorry i cant tell you more

 

What were you experiencing when you were leaking?

 

the smell of gas when i popped the hood lol surprisingly it didnt cause any issues but then again it was a slow drip

 

I dont smell gas at all but is that a reason not to rule it out?

 

no not at all mine had a o ring that went bad, yours could possibly be internal, i would suggest gettin that fuel pressure tester youll be glad you did in the long run and they aint very expensive

 

ok thanks for all your help, wpuld this be the coulpret for my bad mpg

 

anyone else have any input about the catalytic converter? would not having one cause my Jeep to run crappy and lack power?

 

bump

 

Does a 2000 XJ have OBD2, I think so.

If you remove the cat then the downstream O2 sensor wont be reading right and giving the computer bad info, so that might be the cause of the rich condition

You see in OBD2 the downstream (closest to tailpipe) is the king sensor, if its not liking the vapor levels in the exhaust then it will change all sorts of things to get it back to the stoich ratio range which most cars operate at.

 

x2 on this... Put a high flow cat on from summit racing for 99 bucks i think they are.. and then atleast rule that out... I have a 92 that has only 1 o2 and PO removed cat.. and im getting 18 on hwy 14- 15 city...