What could cause one of the cylinders in the engine to go out in an 88 Fiero 6 cylinder

Bad spark plug, plug wire, valve train issue etc. Fieros were not know for their reliability.

so many things here to check...did you get the code????I would pull the spark plug wire from the distributor one at a time. pull one and listen to if the engine bogs down. If it does its firing normal. Put the wire back and try the next one. If you get to one that the idle isnt affected when you pull the wire its not firing that cylinder..start with changing that plug..

Thank you, That gives me some idea of what could be wrong and when the mechanic gives me diagnostic i'll be looking for those issues you listed

Thank you Kelly...that is simple enough and am sure mechanic would be doing that. Again this helps know and understanding the process. Js08016...tune up was also on the list of things to. I don' know what OBD is but I just learned about the"codes". AND hopefully the catalytic converter is NOT damaged. Thanks for your info also.

Again, thank you. This is really helpful. Since the year of the car is 1988 it would just have the OBD. Gaining more knowledge about this quirky Fiero is going help me to understand what the mechanics are talking about.