Hey folks,My 170,000 mile 2000 Cherokee Sport 4x4 is getting 12 MPG. I do drive mostly city, have new tires, and it is great condition. I may have a bit of a lead foot, and a minor oil leak, but this seems a bit low. She idles nice, at like 500-600-RPM. New coolant system FWIW. Thoughts, Thanks.

 

*16-21 mpg is where most people are with the 4.0 engine. Be sure you are "calculating" the exact gas mileage. Miles driven divided by gallons consumed; gotta do the math! Don't try to extrapolate your mileage by miles per tank; it is not particularly accurate. You need a minimum of 3 samples before coming to any conclusion. Keep in mind that mileage will be lower in the winter months if you are in a colder climate for a number of reasons.

*Fresh spark plugs. I like the NGK coppers for the 00-01 ignition system. Verify gap is at .035 Check your air filter. Bottle of a quality fuel injector cleaner (I like Techron) in about 3/4 of a tank of gas can help optimize the fuel injector spray pattern.

*Oxygen sensors can get "lazy" long before they set a check engine light. They have a finite lifespan of between 100k and 150k, depending on engine efficiency.

 

I also have a 2000 xj. I get 18-19 mpg, can't quite seen to break the 20mpg barrier. I would suggest new plugs (NGK V-Power Spark Plug is what I like). Our "coil on plug" jeeps really like NGKs. A new/clean air filter and some Sea Foam in the gas tank should help your gas mileage. Also you may want to make sure your brakes are not dragging.
I am impressed with how fast these XJs are, pretty hard to not put the pedal to the metal occasionally.

 

when was your last tune up???

 

ditto on the O2 sensor, and add a general tune up- plugs wires, cap/rotor, fuel/air filters, pcv, and maybe some seafoam or other carbon/crap breaker-upper. 170k is a pile of miles on any stock sensors still hanging around. freshen it all up and i bet you it gains a couple mpg's

 

Thanks guys, Brakes are new and clean filter, but new plugs are a good start. It has been a while since a tune up. Thanks again, and yes, these XJ's are quick on their feet!

 

i had a 90 accord, i put cheap wires on it and some how spark would jump outta the wires, i could start it up in the dark and you could see sparks jumping all over the engine bay, weirdest thing i have ever seen mechanically, i dont know why i posted this here but, i guess dont get cheap wires

 

The 00-01 has no plug wires. It is a coil pack system. Gotta start with new plugs though. I go no more than 30k on copper plugs!

 

Ordered the NGK's online-2 day shipping. Thanks again.

 

Agreed with tjwalker and whitsonmw, who said do the o2's (both up and downstream, aka bank 1 and bank 2) don't go cheap, either! Just get good, warranted OEM ones. I spent about 110/ea on mine. And don't say I paid too much: my jeep, my budget!! Either way, went from 11 mpg to 18 mpg after doing the o2's...

 

Okay, I am a shade-tree mechanic at best, and see that there are 2 different 02 sensors. Thanks for making sense of it-Thoughts on skill level? Not afraid to try, yet I have no lift/acks or other "pro" stuff.

 

One very common problem that can cause the O2 sensor to read improperly is the cracked exhaust manifold. I'm getting maybe 10mpg and I know that's the problem. It usually cracks where the tubes come together, shine a light there and see if that's the case.

 

O2 sensors, in a perfect world are no biggie, they screw in and out of a bung in the exhaust, BUT!!, they seem to always be darn near welded in there, especially after many years of mud, hot, cold, etc... spray some penetrating oil on them, go take a nap or watch tv for a while, then start wrenching on them. all other tune up stuff is hand tool stuff, shouldnt anything special except a timing light if you decide to check/reset.

 

x2 on the cracked manifold, though neither mine or my dad's are that hard on gas. Another thing is you're city driving. My dad's get's about 10mpg in town but he has gotten 20+ on the highway with 33s and 3.55 gears.
This may be your excuse to get a header

 

Also get some fresh fluids in there, oil, differentials, transfer case, etc