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post #1 of 19 Old February 26th, 2009, 11:06 AM Thread Starter
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What causes engine vibration?

Guys, at low RPM my engine vibrates moderately and it seems like it stops after I get above 2100 RPM or so ...I checked my plugs and they all looked ok. Looked at the motor mounts and they checked out fine too - on top of that I have no CEL so I'm pretty much stumped. I'm workin on a 5.0 fuel injected 1968 coupe that I just got runnin...

Any input or ideas would be great
Thanks a bunch
Tony

Last edited by fatoeknee; February 26th, 2009 at 11:08 AM.
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post #2 of 19 Old February 26th, 2009, 01:01 PM
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is the motor stock? Was it running ok and just started doing this?



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post #3 of 19 Old February 26th, 2009, 01:05 PM
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Quote:
Originally Posted by fatoeknee View Post
Guys, at low RPM my engine vibrates moderately and it seems like it stops after I get above 2100 RPM or so ...I checked my plugs and they all looked ok. Looked at the motor mounts and they checked out fine too - on top of that I have no CEL so I'm pretty much stumped. I'm workin on a 5.0 fuel injected 1968 coupe that I just got runnin...

Any input or ideas would be great
Thanks a bunch
Tony

my cars EXACTLY the same, i think mine is the harmonic balancer cuz i can see some of the rubber like coming out of it

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post #4 of 19 Old February 26th, 2009, 01:11 PM
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+1 or if its a rebuilt motor with a new rotating assembly that was balanced poorly



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post #5 of 19 Old February 26th, 2009, 01:39 PM Thread Starter
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I actually thought it could be a balance issue ...motor has been sitting for some time (probably 4 plus years) ...I'm trying so hard to remember but I think the balancer I bought for it was a new 50 oz replacement along with the flex plate for the c4 being a 50 oz replacement as well - never got them balanced to the motor though. Can a balancer go bad just sitting? LOL - i had to scrape a ton of rust off it just so I could see the timing marks to set timing.
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post #6 of 19 Old February 26th, 2009, 01:56 PM
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i dont think that the balancer could go back but think of all those chmicals building or eating at the block or crank or werever, if it sat for 4 plus years u may have to rebuild it, did u do compression checks to get a idea of the shape the cylenders are in?
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post #7 of 19 Old February 26th, 2009, 03:11 PM
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a stuck lifter


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post #8 of 19 Old March 2nd, 2009, 03:07 PM Thread Starter
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Did a compression check ...all cylinders are within 130-150 suprisingly - any other ideas guys?
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post #9 of 19 Old March 3rd, 2009, 11:31 PM
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If the motor is 28oz balance then it will do the same thing even with a 50oz balancer and flex plate/fly wheel. What year is the motor and if it was rebuilt what was the build balanced at? I have 28, 50 and 0 balanced 302 EFI's and carb'd and if they aren't matched you will get the same thing.

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post #10 of 19 Old March 4th, 2009, 12:04 AM
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wat about ur u-joints? easy check

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post #11 of 19 Old March 4th, 2009, 12:19 AM
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Quote:
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my cars EXACTLY the same, i think mine is the harmonic balancer cuz i can see some of the rubber like coming out of it
ya its time to change yours.. get a sealed one

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post #12 of 19 Old March 4th, 2009, 01:31 AM Thread Starter
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Engine is a 1991 ...Today I noticed a little condensation coming out of my tailpipes on and off and now I'm wondering if that has anything to do with it - the little puffs of smoke that come out are just slightly white but don't smell like antifreeze. Makes me angry I should have bought everything new but I tried to cut corners and bought all used parts
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post #13 of 19 Old March 4th, 2009, 04:27 AM
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are you letting it warm up? it could just be condensation from when you parked it.. drive it around for a lil while and does it still do it?

1990 gt 5.0
Mac Performance 76mm straight shot intake
70mm Accufab tb and egr spacer
Trick Flow Track Heat u/l intake
3.55 gears
MSD distributor, Blaster Coil, and 8.5mm wires
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post #14 of 19 Old March 4th, 2009, 09:57 AM Thread Starter
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Still does it after it's warm
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post #15 of 19 Old March 4th, 2009, 10:23 AM
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do you smell maple syrup?

1990 gt 5.0
Mac Performance 76mm straight shot intake
70mm Accufab tb and egr spacer
Trick Flow Track Heat u/l intake
3.55 gears
MSD distributor, Blaster Coil, and 8.5mm wires
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post #16 of 19 Old March 4th, 2009, 10:47 AM
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1:31 AM
Quote:
Originally Posted by fatoeknee View Post
Engine is a 1991 ...Today I noticed a little condensation coming out of my tailpipes on and off and now I'm wondering if that has anything to do with it - the little puffs of smoke that come out are just slightly white but don't smell like antifreeze. Makes me angry I should have bought everything new but I tried to cut corners and bought all used parts
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do you smell maple syrup?


i have no mustang. so don't listen to anything i say.
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post #17 of 19 Old March 4th, 2009, 10:59 AM
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shhh.. maybe he doesnt know that hot antifreeze smells like maple syrup lol

1990 gt 5.0
Mac Performance 76mm straight shot intake
70mm Accufab tb and egr spacer
Trick Flow Track Heat u/l intake
3.55 gears
MSD distributor, Blaster Coil, and 8.5mm wires
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post #18 of 19 Old March 4th, 2009, 11:03 AM
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Quote:
Originally Posted by BUGMAN View Post
If the motor is 28oz balance then it will do the same thing even with a 50oz balancer and flex plate/fly wheel. What year is the motor and if it was rebuilt what was the build balanced at? I have 28, 50 and 0 balanced 302 EFI's and carb'd and if they aren't matched you will get the same thing.
+1

check out the rubber in your balancer
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post #19 of 19 Old March 4th, 2009, 12:31 PM
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vaccume leak?
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