1993 Grand Prix, starts but if you go on several short trips, it will not start. on 1993 Pontiac Grand Prix

It starts fine when cold or letting it cool down after several short trips, smells gas, runs rough. New spark plugs checked out my mechanic friend who could not find anything in codes -- you can really hear it running rough when following it.

Asked by for the 1993 Pontiac Grand Prix
Just a guess! Black smoke from T-pipe? After running it awhile turn engine off let it sit a minute, pull vacuum hose off of the fuel pressure regulator and check for signs of gas in hose, if any found replace regulator. There should be code(s) stored in computer memory!!!!