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Hi Yall

I am having a problem with my 2000 4.0 L Cherokee Sport, recently my Jeep reached 100,000 miles so I did a partial tune-up on it. I changed the oil and my boyfriend replaced the spark plugs, and afterwards it was sounding and running great. With one exception: my gas mileage went from an avergae 330 miles/gallon to under 220 miles/gallon. I put champion spark plugs (the same brand that I had in before)in and we spaced(gapped) them according to the owners manual. I however did not change the wires because the wires are housed in a "power rail" casing and we werent sure how to go about changing the wires if they are encased. Does anyone know how to change the wires in one of these rails? Do you have to replace the whole rail or just the wires? Could the reduced gas milegae problem be because of the new spark plugs and old wires? PLEASE HELP ME...I am in college and going broke trying to pay for gas for my commmutes to work and back. Any help would be SO greatly apprecaited.  

Ok, let me be the first to say it... if you are really getting 22 miles to the gallon then be a very very happy jeep owner... my 06 Wrangler only gets 20 - 21 with a four...  Highway Miles.
I think if you were getting 33 miles to the gallon you must have been driving your Honda Civic or something.

 

Oh well I meant it was getting 330/Tank not a gallon, which is average for a Cherokee but now I am getting 220/Tank. I would never drive a Honda civic, I'm a Jeep girl.  

oh, well, then I am surprised that somebody smarter than me hasn't posted an answer.
 

I can't help you too much but I have a 97 Grand limited and I had a very similar problem I went from around 330 to around 220...and by around I mean maybe a mile or two off. I have changed the spark plugs twice since then first by the dealer and then myself because my year has different gapping than the rest and I thought they had done them the same as the others by mistake. No avail.
The only thing that makes mine different, makes it much creepier. In Colorado where I use to live I got 330, in michigan 220. I went back to colorado and got 330 again for 3 months, then when I came back to michigan...220. I tried every theory, difference in elevation? nope I should get BETTER gas milage in michigan. Different driving conditions? yeck yes colorado has mountians I drove up all the time=worse milage! all I got were theories on it being tuned for colorado but every mechanic has told me thats not something that is possible with my car.
I just take it as another sign that Michigan is from ***  

Is your timing adjusting properly?  A friend came from sea level to visit me in Colorado and had sever timing problems although his was the opposit of yours.  

Any chance of getting back on topic?  I have the same power rail system with 151,000 miles on it and when I pulled it out, it looks like a sealed unit.  Went to the dealership to see what a new on would cost, but they gave me a set of conventional wires to replace the old ones.  I'm clueless as to how to get into the rail to replace the old wires without damaging it. Has anyone out there performed this procedure?  

Never mind, a little Google'ing revealed that I have a distributorless electrical system.  Apparently, Jeep changed over the electrical system mid-year in 2000.  Here's a great link for anyone who's new to changing their plugs on the newer system: http://www.4x4xplor.com/sparkplug.html  

I recently bought a 2003 Liberty Freedom Edition,78 K miles, 3.7L automatic. I also would like to know about gas mileage, as I am getting 230-240 miles/tank. Mostly city driving....I recently installed a K&N air intake system, but it does not seem to affect the mileage for the better. Any other'03 owners out there? Is that mileage way off base, or do I live with it? Thank you for your input here.  

I have a 2003 Liberty and alerted my dealership about a year ago that mileage per gallon was slipping.  They said it would improve after my first tune-up (60,000 miles).  Well, it didn't.  When the car was new, I got 17.3 mpg; now it's 15.8 mpg.  I've even tried driving differently.  My computer reading above the rear-view mirror says "297 miles left to empty" when I fill up the tank.