1. #1
    blkrubi88's Avatar
    blkrubi88 is offline Senior Member
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    Sudden drop MPG on 02 Liberty!

    OK! This started about two weeks. My wife told me her Liberty was getting terrible gas mileage and when she pulled up at a stop light or sign it would idle real rough. Last week it finally knocked off with her at a stop light and when she finally got it started back up the check engine light was on. I got home and pulled the code, it was for the camshaft and crankshaft positioning senors! I replaced both senors and cleaned the throttle body, it runs smooth. The plugs were replaced about three months ago. It is still only getting about 11/12 MPG. What do I need to check or replace to back to the 17/19 MPG that it used to get?

    It has 3.7 V6. Thanks for any advice you guys can give!

  2. #2
    54cj3b's Avatar
    54cj3b is offline Senior Member
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    Re: Sudden drop MPG on 02 Liberty!

    check your air filter prob needs to be changed ,also full tune up plugs wires cap ect / oil / filter change and a eng flush 3.7s sludge up bad causing major damage to eng I just forked out over $4700. for new eng in my 06 due to major internal damage to eng from slug, eng had 50,000 miles ,also fuel filter couldnt hurt either and clean injectors take care of the precautions before you whined up like me
    see link below
    http://www.jeepz.com/forum/cherokee-...28119-pos.html
    Last edited by 54cj3b; 01-05-2010 at 03:09 PM.
    ALL I OWN ARE JEEPS!

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  3. #3
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    Re: Sudden drop MPG on 02 Liberty!

    Try doing a battery disconnect. This will erase the learned adaptive numerators on the PCM. When the DTC's occured , the PCM will learn a new set of adaptive numerators to compensate for the rough idle and IF this numerators are still stored on the PCM, it will keep running it on a possibly rich condition compensated by the air ratio. Also make sure that you re-set the overhead module for the est. avg. mpg.
    Confucious says: Don't eat the snow where the huskies go!

  4. #4
    blkrubi88's Avatar
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    Re: Sudden drop MPG on 02 Liberty!

    I'll try disconnecting the battery and see what happens. I just found out late last night a good friend of mine has a scan tool we can hook up to see if it is running rich, I just have to wait until he gets over the flu! My wife resets the overhead module every time she fills up. Same friend told me his father-in-laws truck was doing the same thing not to long ago and his ended up being the computer!

  5. #5
    superj's Avatar
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    Re: Sudden drop MPG on 02 Liberty!

    my 02 liberty gets 13 in town on good days. 17 if we are lucky on the highway.

    we lost our engine at 111k and hte mechanic said it had so much sludge in it he was surprised it even ran. we have had it for 11 months so the previous owner didn't take care of it. we are looking at 3k to replace the motor
    no more jeeps at this time. next time it will be a cj with a v8

  6. #6
    54cj3b's Avatar
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    Re: Sudden drop MPG on 02 Liberty!

    heck atleast you saw that many ,we got 50,000 before it took a dump its a comon problem check it out yourself others with same problem http://www.jeepforum.com/forum/f28/j...roblem-543176/
    yup new motor about $4500. to install another $500. any odds end parts needed another $250 ask me how I know. just went through this myself best advise I can give you dump it Quick!!!!!!

    http://www.carcomplaints.com/Jeep/Li..._failure.shtml
    Last edited by 54cj3b; 02-22-2010 at 06:16 PM.
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  7. #7
    DREDnot's Avatar
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    Re: Sudden drop MPG on 02 Liberty!

    I've never heard of any sludge problems on the 3.7
    My wifes 03 has 130,000 miles on the original engine and while I've always used mobil1 and napa gold filters, I never can keep up with the oil changes with the miles she racks up. Best is 5000 miles and once went 11,000 miles between changes.

    Most of the responses in the few cited "3.7L defective/sludge problem" posts are "no problem with mine"
    On of the cited proof threads showed "number of complaints-2"

    Not much of a widespread cover-up.

    Don't buy crap oil and change it more often. It's cheaper in the long run.

  8. #8
    superj's Avatar
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    Re: Sudden drop MPG on 02 Liberty!

    easy to say bif your the original owner. when you buy one alreadt f-ed up you are screwed.

    our plan is replace the motor, drive till jan, sell headache to someone else



    Sent from my MB200 using Tapatalk
    no more jeeps at this time. next time it will be a cj with a v8

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