Rough idle in drive/reverse

Discussion in 'Renegade Chat' started by Eoseitz, Apr 9, 2020.

  1. zuke

    zuke Active Member

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    I knocked the weld nuts off both those front bolts for the skid plate, and replaced them with 3/8" 16 RivNuts, they seem to be much easier to get lined up with the extra plate that came with my RRO winch mount and forward skid plate..

    For you to be experiencing that much vibration, Something solid has to be touching the engine that shouldn't be to transmit it into the body, to me that says it almost has to be an engine/transmission mount, their entire function is to keep that vibration away from the chasis. But it could be something attached to the motor that moves to touch something solid when the transmission is engaged. If we're sure it isn't a bad motor mount, I'd start looking at things attached to the engine that might be hitting/rubbing something.

    The first thing I can think of is the exhaust manifold and downpipe, if that is touching the skidplate before the stainless steel flex pipe, I think that could do it.... another possibility could be a rock or piece of wood trapped near a motor mount, not allowing full travel of the motor mount... but in either of these cases, i would expect the vibration to transmit only in one direction (IE Forward, not reverse, or vis a vis). Could also be the PTU touching something

    It might require securing the vehicle in place, putting it in gear, and searching around under the hood and Renny to see if you can find where the contact is occurring...

    One more crazy thought just occured to me.... Check the rear driveshaft around the middle carrier bearing, especially if you didn't install any spacers in the carrier bearing/skid with the avid lift... That could allow engine vibration to transfer down the driveshaft from the PTU, and transfer to the body there...
     
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  2. Eoseitz

    Eoseitz Member

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    Good call Zuke. I put the 2.5” avid lift on and left the subframe, exhaust and carrier bearing spacers off. I’ll check and see if that’s causing it. Nothing seemed to be hitting when I installed the lift, but maybe it is.
     
  3. zuke

    zuke Active Member

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    While I'm having crazy thoughts, back to a previous one... The Flex pipe in the exhaust hits the Skid plate by design, you could be getting sympathetic vibrations in that loose skid plate...
     
  4. Eoseitz

    Eoseitz Member

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    I retapped the skid plate and tightened it down. Still having the vibrations. I don’t see any header, down pipes or carrier bearings hitting. However, I can’t look at the in gear. They could hit when the Jeep squats down.

    I ran a checked a few sensor values with my scan tool. The first is in park the second in drive. Does anything look out of the ordinary? In drive it looks like it may be running rich. I’m wondering if my air filter doesn’t flow as well as the stock one. May be unrelated.
     
  5. Eoseitz

    Eoseitz Member

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    The first should be in Park, second in Drive and third is diagnostic scan.
     

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  6. Eoseitz

    Eoseitz Member

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    What temp of thermostat are in the Trailhawks? At idle in drive I noticed the temp gauge went up to 217 degrees.
     
  7. Eoseitz

    Eoseitz Member

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    Out of curiosity I pulled my spark plugs. They were set to 0.055 instead of 0.047. Either they wore down a lot since Decemberish or my feeler gauges were wrong. I found my old spark plug gaper and checked them this time. Gas mileage has already improved by 5.5 mpg. It still have the vibration though. It almost has to be the motor mounts. I can’t find anything else wrong.
     
  8. zuke

    zuke Active Member

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    The thermostat is 195, I honestly haven't really watched my temps that much, (I pay more attention to the Trans Temp when wheeling it, and the gas mileage on the road) but the few times I've looked offroad 210~2225 seemed to be the range.
     
  9. zuke

    zuke Active Member

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    Wow, 5.5mpg What we're you getting before that?

    I gotta agree, I think you're back to motor mounts.
     
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  10. Eoseitz

    Eoseitz Member

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    I was at 18.5 mpg. Now I’m at 23.5. That’s mixed highway and town. Can’t wait to see what straight freeway driving is.
     
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  11. Eoseitz

    Eoseitz Member

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    I went ahead and bought the passenger side mount last night. If that doesn’t fix it, I’ll move onto the drivers side.
     
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  12. zuke

    zuke Active Member

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    Nice!
     
  13. Eoseitz

    Eoseitz Member

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    Wow. The new passenger motor mount is way beefier and has a lot more rubber from what I can tell. Now I just have to replace it. Anyone have any tips on supporting the motor and getting the motor mount bolts to line back up?
     
  14. zuke

    zuke Active Member

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    Something like this is really your best bet;

    https://www.amazon.com/dp/B01M7M6NJB/

    You hook it up and spin the handle thingys in the middle to lift the engine, as long as you don't move it's position while you change the mount, everything should stay fairly lined up when you lower it., buy it for $65 dollars, do the job, then sell it locally on FB marketplace for $60.
     
  15. Eoseitz

    Eoseitz Member

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    I saw one of those at harbor freight. I didn’t see anything on the side of the engine to bolt the chains too. What did you hook onto?
     
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  16. zuke

    zuke Active Member

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    I haven't ever done a TigerShark, but your going to want a point toward the front (Right side) of the engine, near the center of mass front to back, but the mount in the rear might force you more to the front (radiator) to lift straight. I'll take a peak at mine tomorrow when I go over to the shop after work and see likely points.
     
  17. zuke

    zuke Active Member

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    OK, So I looked around under mine and I'm not sure I'd bother with a a hoist/bar, I'd take the air box out, then I would take the skid plate off and run a sturdy board on a floor jack up to the is a bulge on the timing cover (Red Arrow) right under where the reverse torque bolts attach at the top of the mount (Blue Box)..
    View attachment upload_2020-5-13_16-41-23.png

    Run the board up there, and and jack it up just until you feel it tighten up, don't lift the vehicle. The other mounts are all still in place, so there really won't be a lot of weight on the board.

    Loosen the three engine side bolts on the mount, and see if the motor even moves before you take them out, if the engine appears to be stable, go ahead and take those three bolts out, then the two on the body side, and take the mount out, and put the new one in..

    If you want to a bar though, I'd Id'take the top bolt on the timing cover out, and attach the chain there (Blue Arrow Below), Red Arrow below is pointing to the timing cover bulge.
    View attachment upload_2020-5-13_16-44-35.png


    Red arrow below is the bulge in the timing cover, Blue arrow is the bolt I'm suggesting if using a support bar,
    View attachment upload_2020-5-13_16-45-30.png


    If you use a bar, it's going to be in the way a lot as you are pulling the motor mount.....
     
    Last edited: May 13, 2020
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  18. zuke

    zuke Active Member

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    Boy, I hate the way this board is handling pics now, You'll have to click each of the attachments to see the picture :(
     
  19. Eoseitz

    Eoseitz Member

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    Wow great write up. Thanks. That is very helpful. I’ll probably try the jack first.
     
  20. Eoseitz

    Eoseitz Member

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    Finally got the mount put on. It was pretty easy. The old one looked fine, but I could easily wiggle it back in forth a couple inches in my hands. The new one is solid. Time to take it up the road and see how she does.
     
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