Originally Posted by DGreenistheBest
I'm assuming that you are talking about the fan in the car, the blower that blows head and AC on you. It kind of sounds like the fan may be locking up and drawing on the battery causing the engine to stumble because the battery power is not constant.
I doubt it has anything to do with your last oil change. I would recommed you take it into a shop because I don't really have an answer for you insofar as a common problem I see. I could be completely wrong about my thoughts, but if it's stalling, you should probably address that.
Pre 1996 (Pre OBD 2 or On Board Diagnostics 2) vehicles are very finicky with their check engine lights. They are not the most reliable when it comes to thinking you have a "real" problem with the car. Just a side note.