1992 Toyota Celica Engine problem

Okay, so I have a 92 Celica GT with about 202k miles on it. I have no problems with this car other then the idle. I know I'm missing one 02 sensor but that's because I couldn't get it to come out of the exhaust manifold. I don't want to break anything so I left it alone for now. I'm not sure if having one 02 sensor only would cause the problem. Anyways the idle goes up to about 1000rpms sometimes a little over, and at times the car will shut off. I can turn it back on immediately after without a problem. Sometimes it turns off as I'm driving and all I do is pop the clutch to turn it back on or just turn the key again. It doesn't do it all the time but its still a problem I want to fix. I took it to a mechanic(I found out that this guy knows nothing about this car) and he said first it could be that the 02 sensors were bad so we changed them out except for one because it wouldn't not come lose, it didn't change a thing. Then he said it was the timing belt so he checked it and it was fine. He has no clue on wtf is going on. I know cleaning the throttle body could help it out as well so that's what I'm going to do next. I just want to get the car running fine so it could pass smog as my tags are going to be due soon. Please if you have any information on this type of situation let me know. Eventually I just going to do a whole engine swap but for now I just need it to get me to work and back without any issues. Feel free to ask questions. Oh and yes the check engine light is on.