I own a 1996 es300. The car was driving fine. All of a sudden it could not go more than 20mph.

Although you did not mention anything about the Check Engine Light, I am going to assume that it is flashing, and that the car has gone into “limp home” mode.

If that is the case, you need to stop driving the car and have it towed to a competent mechanic’s shop for examination, as a flashing CEL indicates that misfire is taking place in the engine. Continuing to drive in that situation will damage the car’s very expensive catalytic converter, and it can also lead to engine damage.

Ditto on @VDCdriver’s comment.

Thanks for the help. One more thing I should add, it has just over 300,000 miles on it and yes the check engine light is on. The acelleration has gotten worse and its kind of sputters and jerks when I first pull out of my neighborhood which is a dangerous intersection. Anything I can do like maybe revving the engine before pulling out so that sputtering is out of its system? I also just had the CV joints replaced bc when I turned the wheel it was making awful clicking sounds but the sounds are still there. any idea what it could be?

Maya–Perhaps I should emphasize this a bit more strongly:

DO NOT DRIVE the car, unless it is for a very short distance to a qualified mechanic.

There are no immediate or easy solutions to the problem, which–from afar–nobody can diagnose properly. All we can say is that you will only wind up with a larger repair bill if you continue to drive it in this condition.

Your solution (revving the engine) is like asking somebody with chest pains to run around the block in order to alleviate his condition. Just as you would likely kill that person, your automotive solution will increase the damage to the engine.

In order to avoid very expensive damage, you need to have a mechanic examine the car, find out which trouble codes have been stored by the car’s OBD system, connect all of his data (based on his visual observances, the info from the OBD system, and his own storehouse of automotive knowledge) in order to come up with the correct fix.

If you can’t currently afford to have a mechanic take care of the problem, then you need to park the car until such time as you have the funds. Any other approach is going to just cost you more money in the long run.

Edited to add:
The OP was “obi”, and the response was from “maya”.
Obi/Maya–Are you the same person posting under two different names?

That CEL (check engine light) is just a kid in class waving her hand trying to get you attention because she has the answer. You need to have the codes read. Some places will read them for FREE. Try Autozone or Advanced Auto Parts. Get the exact code (like P0123) not just their translation into English and post it back here. It would be prudent not to drive it as it is.