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Old 06-20-2012, 09:26 PM   #1
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Default Strange shudder

So I've been noticing a weird shuddering of my engine at idle while in park. It'* not constant, or violent shaking, but it'* there. I cannot discern any sounds changing in the idle when the shudder happens. It does seem kind of rhythmic if that makes sense. Like, every 5-10 seconds. It'* only a slight shudder. I can look at the rubber bushing in the dogbones when it happens and see them wiggling slightly. I also noticed the filter for my K&N CAI vibrating slightly when it happens, since it'* kind of hanging out on the end of the tube, it'* succeptible to vibrations.

Not noticing anything performance wise or any strange vibrations while driving, only when it'* sitting idle in Park. There have been a couple of occasions where I have been sitting in my car after pulling in to my parking spot at work, with the car idling, and kind of felt the shudder ever so slightly in the seat.

Motor mounts? The dogbones look easy enough to replace, but where are the bottom mounts? I looked at Motor Mounts on Rock Auto, and there'* several to choose from. I have no idea which one to pick.

If it'* not a motor mount, what else could it possibly be? I'm hoping I don't have to track down yet ANOTHER vacuum leak. I wish I could buy some sort of "kit" that includes all brand new vacuum tubes and just replace them ALL.

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Old 06-20-2012, 09:32 PM   #2
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I think you and I are experiencing the same shudder. No loss in performance, no lights, bells, dings, whistles or dongs. Just a very slight shudder. Been doing that ever since I swapped from an L36 to a L67. I'm beginning to wonder if its anything to do with the front trans mount.

Yea, someone needs to make a universal vac kit for all bonnevilles.
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Old 06-20-2012, 09:32 PM   #3
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Wanted to add - I do plan on changing the plugs and plug wires next weekend. I'm ordering some PRJ wires and got Autolite 605s to put in. Plan on gapping at .55. Is that right?

This actually brings me to a REALLY stupid question that I'm kind of embarrassed to ask. The gapping tool I bought is the little 50 cent piece sized disc with the gradually increasing edge going around. When I'm sliding the plug around the groove, where do I want to stop the little electrode at on the marks? For example, if gapping to .55, do I want the .55 mark on the very middle of the electrode, on the front edge, or do I go past the middle of the electrode to where the .55 mark is at the back edge is at the mark? I think I'm explaining that to where it'* easily understood. My reason for asking is that I'm thinking if I just put the front of the electrode on the .55 mark, the electrode is wide enough so that the back edge of it is at .53. This leads me to believe that my gap would be slanted, and showing .53.

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Old 06-20-2012, 09:37 PM   #4
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Nope, I understand you very well. Slide the electrode so the edge gets to .55 first. If you center the electrode at .55, the edge will actually be at .60. THEN, flip the plug around and ensure that the other side of the electrode is at .55 also. You wouldn't want a lopsided electrode. But then, that would be real funny if a lopsided sparkplug got you 100MPG.
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Old 06-23-2012, 09:51 AM   #5
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Cool deal. I never thought about flipping the plug or gap tool over, lol.

I hope this idle isn't causing damage. I plan on getting a scangauge 2 soon. Maybe I can monitor fuel trims or ignition or whatever and see if something is going on during that little shimmy. I just don't know what to look for or what should be good or bad, lol. Guess I got some reading up to do.

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Old 06-23-2012, 08:55 PM   #6
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So I took a brief video today. Some of it is hard to see since there'* some mirage showing in the video from the heat off the upper radiator hose,but if you focus on the beam of light on the K&N tube, you can see the shaking. You can also somewhat see it on the radiator hose, and the spark plug wires if you pay attention.

http://s40.photobucket.com/alb.....172945.mp4

Motor mounts? Trans mount? The shaking does seem a little worse on the driver side, but I think that'* just because there'* more stuff over there to notice shaking. Even the throttle body is shaking noticeably. Again, not violently or extreme, but not smooth either. There'* also no discernable difference in the RPMs when it'* doing this.

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Old 06-23-2012, 09:15 PM   #7
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Video not found.
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Old 06-23-2012, 09:27 PM   #8
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Quote:
Originally Posted by Mike1995 View Post
Video not found.
Hmmm...I chose the "direct link" one. Maybe one of these will work -



<embed width="600" height="361" type="application/x-shockwave-flash" allowFullscreen="true" allowNetworking="all" wmode="transparent" src="http://static.photobucket.com/player.swf" flashvars="file=http%3A%2F%2Fvid40.photobucket.com %2Falbums%2Fe210%2FLoudcherokee%2FImpala%2520Brake *%2F20120623_172945.mp4">

http://s40.photobucket.com/albums/e2...623_172945.mp4

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Old 06-23-2012, 09:33 PM   #9
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Yep, mine does the same thing. I think its related to the very bad forward trans mount.
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Old 06-23-2012, 09:37 PM   #10
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Quote:
Originally Posted by Mike1995 View Post
Yep, mine does the same thing. I think its related to the very bad forward trans mount.
Hmmm. Would you recommend Poly mounts or the OEM rubber replacement? If I change one, I might as well change them all, so I'll throw the passenger side motor mount and the upper dogbone bushings in while I'm at it.

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