1988 Toyota Corolla SR5-Check engine light

My check engine light randomly comes on after about 20 minutes or so of driving. It is not on when the car gets turned on but turns on a bit later. When it comes on, I can feel a bit of a jolt from the engine. I read some of the other forums and read that it may be a loose spark plug wire? So I just replaced the entire distributor, rotor, wires, plugs, spark plugs and timing belt all together and it still popped up a check engine light soon after. What could this be, maybe an oxygen sensor? Or do I have to just get the code to reset the check engine light?