92' lesabre check engine light keeps coming on

i have a 92' lesabre which is giving me a hard time right now and i was hoping someone may be able to help me. heres the problem, while driving my car it will run fine then once in awhile ill be going a steady speed and the car will jerk alittle like its kicking into over drive and a few seconds after that the check engine light will come on. it continues to drive fine and awhile later the light will go off. now if i'm at a stop sign and it does it the light will come on and the car will drive but it doesn't want to excellerate it will eventually pick up speed and the light will go off. i have also noticed that if i start the car and the light comes on right away without moving the car it will idle very high you put it into drive and it goes without touching the pedal the light will go off and everything is fine. the car has never died while doing this. the light never stays on more then a few minutes and of course you cant get a reading off of it. i have replaced the position crank sensor and the harmonic balancer when i did that the car ran fine for about 2-3 weeks and then it started over again. also its a 92 car with a 93 motor in it if that matters. any information you have would be greatly apprecited i'm running out of ideas. thank you