1989 Chevy Corsica Car troubles

Hello, I'm having issues with the engine in the car. It started when it was -35, I had the car block heater plugged in, but when I started it the RPMs rose from about 9,000 (usual idle) to about 15,000. When I put the car into drive, the RPMs fell to normal. The car drove fine but after about 15 minutes the rpm started jumping from 0-50,000 and the car eventually stalled. I turned it off and in 5 minutes restarted and was able to drive with no problem. After a while this stopped for a couple of weeks and then resumed with worse symptoms. For the past week when I turn the car on, it starts idling at 15,000 and rises to 35,000 over 1-2 min, when I put it in drive it drops the rpms to 10,000 and I can feel a great push with the engine. I took it into the local shop and the mechanic said it is the engine sensor array. I think its something like that, perhaps connected to the throttle. I took the car out for a drive trying to figure out whats wrong and the engine started reving again so I pulled over, my foot was on the break but I could physically feel the gas being given in the periods of RPM increase as the car rushed forward violently. I came to a stop, shut it off and 5 minutes later its working again! So I'm planning on replacing the whole sensor array in the engine, but I wanted to double check with someone who cant sell me on more repairs :) I would appreciate any input