I have an 85 GS that has a really bad vibration. Not sure what is causing it.
It will start and run but vibrates so much the whole car shakes.
Changed the spark plugs, wires, cap and rotor. Also checked the coils and also checked the motor mounts. Cant figure this out.
Next is I am going to change all the hoses in the rats nest.

Help

 

Check the engine compression as well as tranny mounts

 

check your idle speed too!

 

Might want to post a vid with sound of what you are experiencing. Its hard to say from the
description. My first guess is mounts or missing or maybe compression.

 

Check spark on all four spark plugs.