Thanks for your info Zachh. I had a quick question if you can answer it, will bad cylinders cause it to shake like I mentioned. Before I bought the car cylinders 7 and 8 were loosing compression.
If the compression is in question then a compression check will tell you the story. Be sure to check compression in all cylinders and write down the results. In older / high milage engines the real test of overall good/bad compression is to determine the spread from the highest to lowest reading. A wide spread will lead you to the bad cylinders, especially if 1 or 2 reading are low and the rest are higher and grouped together. The compression of higher milage engine will decrease as the cylinder walls wear, but as long as the spread is small the engine will still perform well enough for every day duty.
Two most common causes are with the valves (seating / burnt) or the piston rings (sticking / broken). A quick check to tell rings or valves; with plugs pulled, squirt a little light weight oil in the suspect plug hole and re-check the compression. Increased reading would suggest a ring problem. No change, then the valves are suspect. As suggested by others, fowled plugs in the lower reading cylinders are indicators of combustion problems,
Bad / broken engine mounts can also cause a lot of vibration, especially if engine isn't running well.
I also had an experience where mice had eaten through some vaccuum lines and spark plug wires, causing hard starting, rough idle & stalling on my 81 during a period it was idle for several weeks and this was in the garage.
I hope these ideas help, in addition to the other possibilities, like bad fuel, or the ignition causes by mis-connected spark plug wires, cracked dist cap. etc.
A word to wise or I'ved done that, been there before; when working on a long list of possible causes, always write down what was found as you go along. It is very easy to start jumping around and losing track of what was good or bad or what was un-clear at the time.
Good Luck!
