Bad Vibrations

[Anonymous]

Hey Guys,

I thas been a while since I have been able to turn a wrench on my Mustang since I have been at school, but I am still being plagued by my engine vibrations a year later. The engine ran great when I bought the car, and through a fit of bad luck, the engine harness fell while I was driving and melted/shorted out on the exhaust causing the car to misfire, and run like crap. It back fired a number of times, and I ultimately had it towed home. I fixed that problem, and then had the transmission rebuilt. Thing is, there is a vibration in the motor that builds as the engine revs. I know it is not the U-joints because it does it while sitting still in park. So far I have replaced the points, plugs, wires, harmonic balancer, rebuilt the carb, and done everthing I can think of. The car still vibrates. I have taken it back to the Transmission shop and they say it is not in the transmission or the torque converter. I can't honetly say if the vibration was there before I took it to the shop or not, but I think it might have been there after I started the car up after fixing the wiring, again not sure. What are some other possible things that would be causing this to happen.

Your help is greatly appreciated.

Jon

 

[MustangSix]

could be a misfire. Get a compression gauge and do a check on all your cylinders to see if you have one that's not up to snuff.

If that checks out, do a double check on the ignition. You can easily spot a plug that's not firing.

 

[80broncoman]

I seem to remember a thread about a dist. cap that had some of the contacts
in the cap "off" from where they should be. If I remember right this was like a year ago. This could cause funky timing and overall roughness. Pop that cap and see if the contacts are evenly spaced apart.

 

[Anonymous]

MustangSix: Compression was actually one of the first things I checked. All the cylinders were equal back when I checked. The variance was less than 5 psi.


80broncoman: I checked this, and it looks normal to me. I also made sure that all the plugs are in the right place to match the stamp on the intake. I also pulled out my shop manual to double check.

The engine doesn't knock or ping, it just vibrates like crazy. Could it backfiring have damaged something that made it out of balance? I have done the start the engine and pull the plugwire and ground it to see if it arcs thing and they all do. This has to be the most baffling problem I have ever had in any car.

Jon

 

[gtm1086]

Crossed spark plug wire????

 

[pedal2themetal45]

seams to me that the viration started after you had the tranny done right :
if it dose this when in nuetral then the only things turnning are the motor, flex-plate, converter, and freewheeling tranny parts..
I would pull the inspection plate on the bell housing and remove the bolts holding the converter on the push it back to the tranny so it clears the flex-plate then start the motor and see if the vibration is steal there. if it is then you have elemanated the tranny and converter. Do you know if they removed the flex-plate? That could also be the prob. it may be bent of out of ballance...
tim

 

[Anonymous]

I can't remember to be honest if it was there after I had the short happen, because after I fixed that I only drove it about 2 miles to the transmission shop. I will try what you said this weekend and will see where I am after that.

 

[Mac]

the next thing I would check would be the motor mounts. Slip a large screw drive or prybar tween the mount and brace and lift up to see if its loose or broken.

 

[pedal2themetal45]

Mac I haddn't thought of that ....I'd also check what Mac said about the motor mounts as well as tranny mount if the motor or the tranny is cocked to one side it well cause a vibration.. you can also check the motor mounts by (sence you have a automatic) putting it in Drive and Reverse and giving it gas with the brake on and watch the motor and see if it lifts to one side or the other.. the motor shouldn't move more that a little bit..
tim..