That car is so old it does not have OBD2 so most common scan tools will not work with it. The older OBD1 diagnostics are much more limited and are manufacturer-specific. This OBD1 scan tool will work with most of them:

Using the above scan tool you should be able to use the check engine light flash method to read any OBD1 codes.

On a 30-year-old car almost anything could be wrong with it, everything has to be considered suspect. Vacuum leaks would be high on the list as decades-old hoses and gaskets deteriorate. Ditto for ignition parts such as distributor cap, rotor, and ignition wires.

Scotty has mentioned in his videos that a worn torque converter can cause vibration at idle and his 1994 Celica does that. It's possible that's what you are experiencing. Worn/collapsed engine mounts will also transmit a lot of vibration and if yours are still original they are most likely bad.

Thanks Chuck, , Are you talking about how many times the check engine light flashes can tell you where the problem would be. I’m guessing only guessing it’s probably like an emission system problem. I had the 2 motor mounts and transmission mount changed a couple years ago. I just put it in neutral to ear up on the vibration. I’ll check the vacuum lines and like you said it’s 30 years old. It runs great everything works, all the windows, a/c , radio. It’s my extra car. In reality with a 30 year old car it only has 200,000 miles. I can live with the issues. Hoping it might be something simple. Thank you for the help