Jeep Losing Fuel Mileage?

TapouT

Well-Known Member
Joined
Oct 5, 2008
Location
Hickory nc
I bought my 1998 Jeep Grand Cherokee about 4 months ago. It has the 5.2 V8 in it. It had a 3" lift and 31" tires on it when I bought it. When I would fill up when i first got the Jeep on the overhead console it would read anywhere from 330-340 miles DTE(distance to empty). Now when I fill up it's going to about 244 miles and that's as high as it will go. I've recently done a complete tune up (plugs, wires, dist cap and rotor button, air filter) and it didn't help any. My gas isn't going near as far as it used to. The jeep is still lifted 3" but it has 33/12.50/15 tires on it now rather than 31's when I first bought it. Does the computer re-calculate for bigger tires? I wouldn't think that it would. The Jeep also runs rough when in drive sitting at a stoplight, not sure what the deal is there. I've replaced the IAC but that hasn't helped. Any help would be greatly appreciated because I feel like I'm just pissing money away now when I fill up. Thanks for the help!
 
going from 31 to 33 is what it is if you left your stock gears
the computer will not re-calculate for bigger tires
also you are driving more miles than what the speedomter is saying

running badly maybe fuel filter????????????????
 
part of it is your speedometer gearing hasn't been corrected for the tires-with a little internet searching & some math, it should be about $20 for a new speedo drive gear-that will fix the display to read actual. it sounds like your idle roughness is a symptom of something else- without hearing it run, i can't even take a good guess at it
 
I'm not sure what the rough idle could be..driving me pretty crazy though. I put a new Iac on it awhile back and it did fine and then last week I unhooked the battery and touched both terminals together to drain the battery out/reset it and see if that was what was causing my DTE display to read like that and it didn't fix it and now it has ran rough ever since. It ran great before. I didn't think resetting the computer would cause it to run rough like it is.
 
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