1994 Mazda 626 ES-V6, check-engine light at highway speeds, OBD-1

I have a 94' 626 ES-V6. At high-way speeds my check engine light comes on and then goes off after a few minutes. Hard acceleration seems to trigger it quicker, but if I go 80mph it comes on regardless. If I get off the highway and come to a stop the light goes out. I have OBD-1 and I have tested my vehicle, but it always blinks the code that everything is fine. Does anyone know if OBD-1 codes are stored and should be retrievable after the engine-light goes out? I have never been able to turn my car off while the check-engine light remained on and test the OBD-1. I would have to pull off the highway, stop, and turn off the car very, very quickly. Is this the only way I can retrieve the trouble code from the OBD-1? Does anyone have an idea of what causes the check-engine light to come on in the first place?

ANY and ALL suggestions would be GREATLY APPRECIATED!