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Tune up didn't resolve hesitation issue

Discussion in 'Liberty' started by Dd14, Jul 4, 2018.

  1. Jul 4, 2018 at 5:56 AM
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    Dd14

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    Dd14 [OP] Member

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    04 Liberty has some hesitation when driving, rpms drop and a little hesitation. Mechanic said tune up would correct issue and mainly changed plugs. Issue still occurring should plug coils have been changed also?
     
    Dd14, Jul 4, 2018
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  2. Jul 4, 2018 at 7:54 AM
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    Awrench

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    Awrench Well-Known Member

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    to me a technician suggesting a TUNE UP is a red flag.
    There is no longer any tuning to be done... The large diagnostic "sun" machines of yesterday are incorporated into your OBD system... OBD is also constantly monitoring and adjusting settings.

    A scanner should be used to observe the system,looking at codes and live data.
     
    Awrench, Jul 4, 2018
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  3. Jul 4, 2018 at 8:27 AM
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    Dd14

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    Dd14 [OP] Member

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    No codes by scanner. Another thread mentioned the plug coils.
     
    Dd14, Jul 4, 2018
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  4. Jul 4, 2018 at 9:34 AM
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    chris4x4

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    chris4x4 With sufficient thrust, pigs fly just fine Moderator

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    Welcome! Anything in particular going on before this happens?
     
    chris4x4, Jul 4, 2018
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  5. Jul 4, 2018 at 9:59 AM
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    aggrex

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    aggrex Well-Known Member

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    Welcome! How long has this problem been occurring? Reviewed all the basic stuff yet?....like bad gas, clogged air filter, vacuum leaks, plug wires, etc? What's a tuneup?
     
    aggrex, Jul 4, 2018
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  6. Jul 4, 2018 at 10:17 AM
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    Dd14

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    Dd14 [OP] Member

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    Hesitation usually happens about 30-40 mph, rpm drops you can feel it but when gas pedal pressed works through.Gas mileage has decreased dramatically in last month or so. Tune up? IK archaic term, all spark plugs only changed out.
     
    Dd14, Jul 4, 2018
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  7. Jul 4, 2018 at 10:21 AM
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    chris4x4

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    chris4x4 With sufficient thrust, pigs fly just fine Moderator

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    I would check the basics. Air filter, MAF/MAP clean, etc
     
    chris4x4, Jul 4, 2018
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  8. Jul 4, 2018 at 11:23 AM
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    Awrench

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    Awrench Well-Known Member

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    Did you use a scanner to check for codes - NOT key on off trick. DBL checking.
    With scanner what is ECT, Fuel Trims, o2 sensor voltages, Map,

    If no codes check and no data - check fuel pressure as there is no direct monitoring of fuel pressure...
     
    Awrench, Jul 4, 2018
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  9. Jul 4, 2018 at 9:38 PM
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    OFFGRID

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    OFFGRID Well-Known Member

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    I had a 99 and 2002 dodge truck do this when I crossed 100,000 miles. I had to have the dealer flash my computer to correct it. At 200,000 it happened again on my 99 and I bought a programmer for it and that fixed it. I sold it before it reached 300,000 miles and my 2002 never saw 200,000.
     
    OFFGRID, Jul 4, 2018
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  10. Jul 5, 2018 at 9:25 AM
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    Dd14

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    Dd14 [OP] Member

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    Now throwing code P0839. Would the sensor cause issues?
     
    Dd14, Jul 5, 2018
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  11. Jul 5, 2018 at 10:13 AM
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    Awrench

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    Awrench Well-Known Member

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    confirm - 04 liberty 3.7L automatic4 wd showing p0839?
    List ALL codes.


    You used a SCANNER- ?

    a trnasfer case issue - P0839-4WD MODE SENSOR HIGH

    A scanner will make this easy, any other codes ? check freeze frame, look at sensor voltages...

    I suspect other codes.issues or lights

    POSSIBLE CAUSES
    TRANSFER CASE POSITION SENSOR INPUT CIRCUIT OPEN
    TRANSFER CASE POSITION SENSOR INPUT CIRCUIT SHORT TO VOLTAGE TRANSFER CASE POSITION SENSOR
    POWERTRAIN/ENGINE CONTROL MODULE
    INTERMITTENT OPERATION
     
    Awrench, Jul 5, 2018
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  12. Jul 5, 2018 at 10:19 AM
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    Dd14

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    Dd14 [OP] Member

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    Key check. No other codes
     
    Dd14, Jul 5, 2018
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  13. Jul 5, 2018 at 10:28 AM
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    Awrench

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    Awrench Well-Known Member

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    Ok lets get serious SCAN !

    Key trick will not show ALL codes All modules!
    The live data is needed to make this easy.
     
    Awrench, Jul 5, 2018
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