Oldsmobile/Buick Repair: vibration at acceleration, buick lesabre, broken spring

Question
Van,
I have a 1992 Buick LeSabre that has had over $3000.00 worth of work done in the last 6 months and no one is getting to the root of the problem.  Motor mounts re-done, ignition coil, cam sensor, injectors, various pumps, fuel filter, harmonic balancer, etc... Now the car vibrates even at idle, and it is very difficult to get up to speed.  Vibrates and you have to feather the gas to work your way up.  Computer code throws cam as problem, but that has been replaced. this originally all started with a stalling problem. I am losing my mind and now have more invested then what the car is worth!! Please help me.

Answer
Hello Mystie,
I had one that acted similar. it would shudder, especially when it shifted into overdrive, but feathering the throttle seemed to help.
Mine turned out to be a broken spring on one of the valves. Isolated the cylinder with a compression test, then was able to replace the broken spring without pulling the head, by using air pressure in the spark plug hole to hold the valves closed.
May not be your problem, but sounds similar.
Van