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Thread: pinpointing engine vibration

  1. #1
    Join Date
    Apr 2015
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    Illinois
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    pinpointing engine vibration

    Hey everyone, my engine recently started vibrating more than normal. I do have solid rubber motor mounts and I put a Powerbond (Dayco) harmonic balancer on it back at the end of December and it has run pretty smooth since. Within the past week the engine vibrations have gotten noticeably worse (mostly between 2,000-3,000 rpm) and you can feel it shake the whole car when stationary and even driving.

    I changed the oil yesterday and checked the balancer bolt, nothing seemed out of the ordinary, but it still vibrates pretty good. I haven't noticed any lack of power or drop in fuel mileage either.

    Any thoughts on what to check next? I'm thinking maybe the balancer is already shot?

    The car is an 89 XR7.

  2. #2
    Join Date
    Dec 2007
    Location
    Salem, OR
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    6,288
    Auto or manual trans?

    Messed with the plugs/wires/coil recently?

  3. #3
    Join Date
    Apr 2015
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    Illinois
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    It's a 5-speed manual and no codes are being thrown. I have not messed with the ignition system.

  4. #4
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    Dec 2007
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    Quote Originally Posted by tberger06 View Post
    you can feel it shake the whole car when stationary and even driving.
    If that means regardless of clutch depressed or not, I'd suspect the balancer, but we're told the PBs don't fail - did you check the center bolt? Might need to pull it to see if the key sheared, etc.

  5. #5
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    Illinois
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    Quote Originally Posted by KMT View Post
    If that means regardless of clutch depressed or not, I'd suspect the balancer, but we're told the PBs don't fail - did you check the center bolt? Might need to pull it to see if the key sheared, etc.
    I held the clutch in and put it in gear while sitting in the driveway and it didn't change the vibration at all.

    If the key sheared, wouldn't that throw off my timing as well?

  6. #6
    Join Date
    Dec 2007
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    Yes, perhaps adding to engine vibrations, but the computer might be trying it's best to mask timing change, depending on how minor/major.

    The only way to know/eliminate as suspect, is to manually time the engine using the balancer marks, etc. while validating center bolt, etc.

    See this previous thread for discussion: http://www.sccoa.com/forums/showthre...lt-break-first

    Might be a pressure plate issue/thrown weight. Might be a trans mount failure. Might be motor mounts...if you watch the engine, does it rock badly when someone revs it in neutral?
    Last edited by KMT; 05-09-2017 at 12:01 PM. Reason: added link

  7. #7
    Join Date
    Nov 2016
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    PNW
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    226
    Are K-member bolts to 100 ft/lb torque? E-18 female socket required.
    All suspension bolts checked to factory spec is wise as well.

    Creighton
    Last edited by Creighton; 04-24-2017 at 08:06 PM.

  8. #8
    Join Date
    Jul 2005
    Posts
    380
    Good afternoon


    I would check the harmonic balancer pulley bolts. Re-torque the four bolts. Start car and check for a wobble. I have had a bolt back off causing the same issue.



    Good Luck.

  9. #9
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    Apr 2015
    Location
    Illinois
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    I'll get it up on a lift and check all that stuff hopefully this weekend. Thanks for all the suggestions.

  10. #10
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    Apr 2015
    Location
    Illinois
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    I removed the harmonic balancer today and nothing was wrong. The balancer, crank, and key were all fine.

    We put the car up in the air on the lift with my friend inside and had him start it up and hit the throttle while I looked at it from underneath. The flywheel turned perfectly straight.

    The motor mounts are in great shape and the engine does not rock side to side under throttle.

    With the car off we turned it over by hand and looked at all the clutch bolts. They were all present and none had backed off. We also stuck a flexible magnet down inside near the bottom of the flywheel to see if there were any balancing weights or pieces of metal, but the magnet came out clean.

    The only possibility left that I can think of is a loose flywheel bolt (not very likely since it doesn't have any wobble), the flywheel became unbalanced somehow (but how?), or something internal to the engine is out of whack (I'm not really sure what that would be though). It still has no codes and runs great.

    I'm debating on just driving it until something gives out.
    Last edited by tberger06; 04-29-2017 at 07:16 PM.

  11. #11
    Join Date
    Jul 2005
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    380
    Good evening

    If you found no defects at the engine next step would be the drive train. Specifically the drive shaft and or bad transmission mount. Do you feel a slight "bang" when in reverse? If so check the four drive shaft mount bolts for torque. They have been known to back off. If no defects with the transmission mount/drive shaft bolts suspect driveshaft universal joint.

    Have you see this link: http://www.sccoa.com/forums/showthre...searched-first




    Good Luck.

  12. #12
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    Quote Originally Posted by sam jones View Post
    Good evening

    If you found no defects at the engine next step would be the drive train. Specifically the drive shaft and or bad transmission mount. Do you feel a slight "bang" when in reverse? If so check the four drive shaft mount bolts for torque. They have been known to back off. If no defects with the transmission mount/drive shaft bolts suspect driveshaft universal joint.

    Have you see this link: http://www.sccoa.com/forums/showthre...searched-first




    Good Luck.
    This happens when stationary and out of gear, so I can eliminate anything after the transmission as a possible cause.

  13. #13
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    Jul 2005
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    Quote Originally Posted by tberger06 View Post
    This happens when stationary and out of gear, so I can eliminate anything after the transmission as a possible cause.
    Good evening


    Sorry I did not understand the condition. You might want to try troubleshooting the drive/accessory system. Disconnect the belts one at a time start the car and see if this will eliminate the vibration issue.

  14. #14
    Join Date
    Apr 2002
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    Madison, Ohio
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    17,532
    Anything can fail. BHJ balancers have failed in the past also. I haven't see the steel hubs break, but the elastomer can fail and I've seen them out of round.

    But more on point - Never seen a keyway fail. Ever. It's a long key with tons of engagement. Probably the last thing I'd ever suspect, particularly on an iron balancer.

    If the ring turns, it can only do so if the elastomer fails, but that doesn't affect timing as the reluctor ring is bolted to the hub, not the ring. The only way timing can be affected is if the hub shears. Never seen that on anything other than an aluminum hub. Ever.

    The hub and ring are both neutral balance. If one DID shift, it would not likely noticeably affect balance, however if something did happen severe enough to cause that to happen, you have much bigger problems than a failed balancer. The balancer would most likely be the victim in this case, not the cause. You can check the elastomer for resilience. They get work hardened over time which is another reason why factory balancers tend to fail - the OE rubber gets rock hard, cracks, and literally starts to fall out. PB balancers are made by Dayco, yeah the worlds largest HB manufacturer. I've spoken with their engineers, they claim their elastomer will literally pretty much never harden. Better material than 1989-95 OE.

    That being said, a broken mount could transmit more vibration into the car, or anything binding the motor (a wrench stuck under the oil pan, who knows?). But if you've eliminated all external factors, it could be pointing to an internal engine problem - bent connecting rod or crankshaft. That is something I've seen many times.
    Quote Originally Posted by Miller View Post
    Ya thats why i tape mine down. People think its bc i dont have a moonroof seal (which is true) but its really to keep my roof from ripping off .
    Email me here.

  15. #15
    Join Date
    Apr 2015
    Location
    Illinois
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    I think I'll get a replacement balancer to put on it. This way I can eliminate the balancer if it still vibrates with the new one.

    In the event it still vibrates, I guess I'll need to pull the engine and tear it down. My concern is the engine only has 23k miles on it after a rebuild by Jasper, which seems way too soon.
    Last edited by tberger06; 05-09-2017 at 11:06 AM.

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