I would need your help. I just got this 1990 GT-S. it is a nice car but if i turn on the engine (RPm starts at 1600 and goes down to 800 after the engine heats up) the whole car is shaking. It has some strange vibrations and it last when i drive, all the plastics and mirrors ar shaking.. Any idea what`s wrong???

If you car shakes when you are not driving, likely something is not balanced.

Check your engine mounts. Sounds like your engine is no longer held against the frame in all locations.

If you rev your engine and it runs rough, you will need a new timing belt. Otherwise check the mounts.