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  1. #1
    Member Mark 318 ita's Avatar
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    grand chero is shaking

    Hi guys, these days aren't too happy, i have some problems with the grand chero :
    is a 98 limidted 318,
    when i'm not moving, like to a stop signal, and i'm in D with the brake applied the zj is "shaking" more and more.
    It starts slowly with little vibes, but after few seconds (like 2-3 secs) shakes more and more...are some vibes that grows slowly.
    I noticed that if i press the gas pedal lightly (like 1200-1300 rpms) and the brake pedal at the same time those vibes stop.
    While i'm pressing both pedals i can feel the car "loading" but no more vibes.

    any ideas? advices?

    thanks, i hope i wrote clearly...


  2. #2
    im super special x10radsponge's Avatar
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    So, when in park there are no vibrations? How about neutral and the other gears while idling?

  3. #3
    Member Mark 318 ita's Avatar
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    sorry, i forgot to say that: no in P and N no vibes...

    other gears yes, some little at about 95-97 kmh, so at about 60mih (mih?)
    Last edited by Mark 318 ita; 04-05-2013 at 10:45 AM.

  4. #4
    Modfag Saleen4971's Avatar
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    Motor mounts are a quick easy check, and they can cause some weird vibes
    Ross
    1998 Grand Cherokee 5.9 Limited
    MPP Headers - Thunderbolt Metallic Cat - 3" Mag catback - EBC Brakes w/ drilled Rotors - 4bbl M1 - Vortech 12psi - Built trans & 2900 stall - Ford 8.8 - Addco & Hellwig Sways - Poly Bushings - H&R Springs - Grabber UHP Tires - Alpine/Infinity Stereo - FX-R BiXenon Retrofit

  5. #5
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    Quote Originally Posted by Saleen4971 View Post
    Motor mounts are a quick easy check, and they can cause some weird vibes
    X2
    That's what I would check first.

  6. #6
    Member Mark 318 ita's Avatar
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    no sorry guys, engine and tranny mounts are now, 6 months old...they are prothane

  7. #7
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    Hmmm?

  8. #8
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    Could it be some bizarro torque converter issue?
    '98 Grand 5.9 "Black Pearl" totaled
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    "No Officer, all four tire tracks are mine, it WAS all wheel drive......yes ma'am Im aware this structure is normally used to 'park' cars"

  9. #9
    Slick Member Moparboy72's Avatar
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    I feel like I may have the same issue as you; How many miles/KM on your Jeep?

    Did you have this shaking/vibration before the Prothane motor mounts?

  10. #10
    Member Mark 318 ita's Avatar
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    Hi,
    1)if it is the TQ...how can i check it?
    2)jeep has 210000 km (131000miles) and, no, no vibes after new mounts(just small vibes in the very first days 6 months ago)...these vibes are pretty new. They started a few days ago.

    thanks guys for the help, i appreciate.

  11. #11
    Member Mark 318 ita's Avatar
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    hi guys, today i noticed some light vibes at about 38-39 mph, only if i'm accelerating...

    any ideas?

    thanks

  12. #12
    Member Mark 318 ita's Avatar
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    i don't understand, sometimes it shakes...some other times it does not...

  13. #13
    Member ZJ-John's Avatar
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    Check your harmonic balancer.

  14. #14
    Member Mark 318 ita's Avatar
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    10.4 thanks, i'll check it out.

  15. #15
    Member Mark 318 ita's Avatar
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    the mechanic said that is the tranny, but it is "almost" normal because of the 211000 km, that i warry too much...

  16. #16
    Slick Member Moparboy72's Avatar
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    Can you feel these vibrations in "N" at idle or off idle speeds (1200-1500?)?
    If so you may want to check the compression of the engine (as long as the mounts check out).

  17. #17
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    If I miss read sorry but if u said it vibrates when ur braking could it be warped rotors?

  18. #18
    Member Mark 318 ita's Avatar
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    @moparboy: nope, N is fine

    @bumpindude: no probably i explained myself not well, sorry my fault. What i meant to say was that if i press the brake pedal and the gas pedal (the gas pedal lightly) at the same time there are no more vibes.

  19. #19
    Forum CONDUCTOR Man Z88Z's Avatar
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    Quote Originally Posted by ZJ-John View Post
    Check your harmonic balancer.
    That's a good thing to check too. Our balancers are know for separating at the rubber section.

    I'd check Ujoints. CV joints and maybe tire balance too. Those can cause some "sometimes it's there, sometimes it isn't" vibes.

    Maybe check the input flanges at the front and rear diffs too.



    Quote Originally Posted by Mark 318 ita View Post
    the mechanic said that is the tranny, .......
    I don't think I'm buying that as an explanation.

    If you think about how auto trannies are built and the parts that could wear...

    I think it would have to be pretty seriously messed up to produce shaking

  20. #20
    Member Mark 318 ita's Avatar
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    hi, thanks for these advices...next days i'll check those things out for sure.

    so are you saying that the tranny is not guilty?
    edit: shifting is almost fine, i say almost because sometimes (rarely) the tranny does not shift well form 2nd to 3rd.
    edit.2:i remembered that about 10.000 miles ago we opened the oil pan of the tranny and the magned inside the pan was pretty clean, without emery and we put new oil. we checked last week and the oil was pretty clean after 10000 miles.
    Last edited by Mark 318 ita; 04-29-2013 at 08:48 AM.

  21. #21
    Slick Member Moparboy72's Avatar
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    What is the history of the following items (original/replaced/cleaned..):

    Intake Plenum Gasket
    IAC Solenoid/Motor
    TPS
    Throttle body

  22. #22
    Member Mark 318 ita's Avatar
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    uumm,
    intake plenum gasked: i have no idea, not ever touched it since i have the car (i bought it almost 4 years ago), but the car is "eating" little engine oil. About 1kg (2lbs) in 7000 miles;
    IAC Solenoid: same story;
    TPS: same story;
    Throttle body: it should be clean, because a couple of years ago my mechanic told me that he cleaned it up and changed the seal. After that one year ago i he put the new hat (the spectre one).

    now car has 212000 km, that should be around 140000 miles.

    thanks for helping me out

  23. #23
    im super special x10radsponge's Avatar
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    If you look down the throttle body while opened, it should look nice and dry and clean. If you look and see a bunch of oil residue. Then that indicates a bad plenum gasket and could result in bad mileage, pinging, rough idle as oil is getting into the air/fuel mixture.

  24. #24
    im super special x10radsponge's Avatar
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    This is what one with a blown or bad gasket looks like.
    IMG_0455.jpgIMG_0459.jpgIMG_0460.jpg

  25. #25
    Member Mark 318 ita's Avatar
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    Quote Originally Posted by x10radsponge View Post
    If you look down the throttle body while opened, it should look nice and dry and clean. If you look and see a bunch of oil residue. Then that indicates a bad plenum gasket and could result in bad mileage, pinging, rough idle as oil is getting into the air/fuel mixture.
    nope, last time it was clean...

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