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Help! Really poor fuel mileage. 2000 Cherokee Limited

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achildofthesky
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Joined: 10 Feb 2006
Location: USA

PostPosted: Fri Feb 10, 2006 7:45 am    Post subject: Help! Really poor fuel mileage. 2000 Cherokee Limited Reply with quote

Hey there all. I am new to the forum and really need some help with my 2000 Cherokee Limited. It is a 4.0l, auto trans 4x4 with about 65kmi and runs quite strong with plenty of power, but the rig gets really bad mileage (maybe 210 miles to a full tank!). It doesn't sputter of jerk and acceleration is immediate. The tailpipe shows signs of running really rich (it burns no oil). I have not seen any check engine lights. It has a new air filter. This rig came from SLC, Utah and is now in NW Arkansas (elevation 1350 msl).

Have any of you experienced this before and what should I be looking for as far as troubleshooting? Thanks in advance for the space and time.

achildofthesky
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ThePhantum
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PostPosted: Fri Feb 10, 2006 8:57 am    Post subject: Reply with quote

I would change the spark plugs (the 00's don't have wires, a cap or a rotor) and disconnect the battery for an hour or so. The ECM runs the engine based off of historical data. Since it's now in a higher altitude, the old data should be cleared so that the ECM can build a new set based of the conditions it's running in now.

After it's reset, it will take a few hundred miles for the ECM to gather new data. It might be as simple as that.

HTH
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achildofthesky
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Joined: 10 Feb 2006
Location: USA

PostPosted: Sun Feb 12, 2006 2:38 pm    Post subject: Thanks for the tip... Reply with quote

I changed the plugs yesterday. The plugs looked decent color wise but the gap had worn to over .050 on all and 1 at about .060. I will thry the disco on the battery for a rebasing calibration. Thanks again.
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Code3TJ
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PostPosted: Mon Feb 13, 2006 1:18 am    Post subject: Reply with quote

You said 210 miles to a tank - how many gallons is your tank? Have you averaged several tanks to see what exactly you're getting?
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achildofthesky
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Joined: 10 Feb 2006
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PostPosted: Mon Feb 13, 2006 5:57 am    Post subject: Poor Fuel Mileage... Reply with quote

The tank is a 20 gallon tank. I will be going on a ski trip to Colorado in a week or so that is about 850 1 way and will carefully check the mileage. I expect it will be a lot better at a steady speed on the highway but for the day to day driving OMG it is really the worst mileage vehicle I have ever driven. Worse even than an FJ 60 Landcruiser I used to have...

I also posted about the possibility of swapping the auto transmission for a manual ( I hate Auto transmissions). I would greatly prefer a 5 or 6 speed even if it didn't improve things much mileage wise. Any comments there?

Somewhere I saw a trick for cutting down a tube in the fuel tank to increase the capacity you can put in it. I recall this to be for the 4 cylinder with a 15 gallon or so tank. I wonder if this mod might work for a 20 gallon tank too to extend the range of the XJ a bit.
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ThePhantum
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PostPosted: Mon Feb 13, 2006 10:29 am    Post subject: Reply with quote

Yea, it's a 20.2 gallon tank. Even my gas guzzling XJ gets 245-255 miles to a tank. When it was stock, it got just over 300, so 210 is low.
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JeepinNH
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Joined: 13 Sep 2005
Location: New Hampshire

PostPosted: Mon Feb 13, 2006 3:26 pm    Post subject: ouch Reply with quote

Wow, that's really bad MPG's. My stock unloaded XJ runs between 15 and 18 MPG's but better on the highway. Maybe it's time to run fuel injector cleaner through it. Also, not all gas is created equal. You may want to try a couple different stations/brands.
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ThePhantum
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PostPosted: Mon Feb 13, 2006 9:12 pm    Post subject: Reply with quote

If you're refering to 210 miles on a tank...yea, that's horrible.

If you're referring to mine...it ain't stock. Plus, I'm dragging between 400 & 500lbs in gear, tools, skid plates, roof rack (a spare tire and hi lift on the roof are excellent for aerodynamics), winch and bumper (another aero bonus). The MT's on all 4 corners don't help much either. Even with all that I still average around 13 mpg...not too shabby. Wink
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jppilot61
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PostPosted: Tue Feb 14, 2006 3:32 am    Post subject: Reply with quote

I noticed that after a trip to Paragon, where my 92 Stock XJ took a beating (severely saggy rear springs!) that my range decreased drastically! Of course there were tremendous dents in the gas tank , reducing its capacity to about 2/3rds of what it should have been!(thankfully it did not leak and made it back to Virginia under its own power)!

Have since purchased replacement tank and a 2nd hand Gas tank skid. I will be installing it soon.

Hopefully yours is JUST a sensor!

But, heck I got a skid plate outta it and MJ didn't argue about lifting it even though she can barely get into it now it!
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Last edited by jppilot61 on Fri Mar 17, 2006 11:31 am; edited 1 time in total
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achildofthesky
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Joined: 10 Feb 2006
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PostPosted: Tue Feb 14, 2006 5:30 am    Post subject: Really poor mileage... Reply with quote

Well, I disconnected the battery yesterday for about 5 minutes and while I was at it cleaned tha crap off the terminal then reconnected and filled up with gas at a different place. The tank doesn't seem damaged as the pump shut off at around 18 gallons by its self with the needle showing midway between mt and 1/8 tank. I topped it as much as I could get in this time (got it to 20.3!) and I will refill again next time with as much as I can get in. Also, I am trying to drive in the same pretty much manner that I have been doing since we got the rig.

Going in for an alignment tomorrow and will ask the service guy at the Jeep dealer for any suggestions... The guy at Autozone checked for fault codes after I changed the plugs (champion 4421 truck plugs) and found none and I did the key on/off while holding the trip reset an there were no codes shown on that either. Maybe it was worn plugs with the gaps all over .050 and one at over .060... I will have to wait and see for a while untill the fuel burns off some.

The vehicle is stock/undamaged in all respects with 79k miles, 225/70 16's and is an auto/4x4 (2wd/4wdpart time/4wd full time/4wd low xfer case) with a towing hitch that looks OEM installed and is definately in 2wd for checking the mileage. The 4wd engagement is smooth and positive, I verified it on a nice little grassy hill. Also with a new fram air filter.


Any other comments welcome. Are Cherokees prone to vacuum leaks
or the like??? Thanks again in advance for the help.
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ThePhantum
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PostPosted: Tue Feb 14, 2006 8:46 am    Post subject: Reply with quote

Those wide plug gaps might have been causing the problem. A 5 minute loss of power might not be enough to reset the ECM. I would leave it disconnected for 30 minutes or so.

As far as vacuum leaks, the lines coming from the vac reservior are prone to cracking...but normally that affects things like the vent ducting, not gas milage.
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JeepinNH
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Joined: 13 Sep 2005
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PostPosted: Tue Feb 14, 2006 6:38 pm    Post subject: mileage Reply with quote

Phantum, when I posted "Wow, that's really bad MPG's" I was referring to the original poster. I realize your XJ is modified which of course reduces the MPGs. 210mi on 20 gallon tank is sad for a stock XJ.
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dadstoys2
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Joined: 08 Nov 2005
Location: York, PA

PostPosted: Wed Feb 15, 2006 10:40 pm    Post subject: Reply with quote

Well my old 2.8 in my 85 XJ was only getting about 12mpg and it was stock. But that was cause it had no balls... Had to put the pedal to the floor all the time just to keep up with traffic.
But now I have a 3.1 with 41k on it and I'm almost done with the swap. I should get a good bit better than the 12mph that I was getting. Maybe closer to 16mpg is what I am hoping for.
I only have an 11.5gal tank in mine.
~Rich
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achildofthesky
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Joined: 10 Feb 2006
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PostPosted: Wed Feb 22, 2006 3:12 pm    Post subject: Well up to 285 miles on this tank full after changing plugs. Reply with quote

I may have solved at the least a portion of the crappy mileage. Now it is merely bad at about 285 miles till the fuel light came on on a topped up tank. I am going on a trip out west tomorrow of about 850 miles 1 way all highway and will try the old 2-3 oz of acetone to the tank and see if it gives me a bump in mileage on the highway... I will post my findings next week.

It would seem that the plug change has really helped. The gaps on the ones I removed all were over .050 - .055 and one was at .065. They were prolly the originals, I reckon...

Thanks for the help folks.

achildofthesky
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NiX94XJ
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Joined: 05 Oct 2005
Location: Excelsior, Minnesota

PostPosted: Wed Feb 22, 2006 5:47 pm    Post subject: Reply with quote

I have the same problem, granted mine is lifted about 5" with 31" tires.. It's a 94, auto trans, 4x4 with 114K miles. But the mileage still really bad, should do much better than that. I got about 285 or so when it was stock. I'm a mechanic and i cant find anything wrong with it, pulled 2 plugs out and they're relatively new, gapped correctly, cap rotor and wires all look good. Runs pretty smooth. i just put a new fuel filter in it last week and that didnt seem to change a bit, the old one wasn't plugged up too bad. I changed out both diffs, x-fer case, trans, and engine with synthetic oils. No change. I think I might try just throwin plugs wires cap and rot in it this week, maybe try hookin up the injector cleaner, I'm all out of ideas on this one.. Anyone else find a solution??
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