I have a 2.3L 1990 mustang i was daily driving for about a year. I left it sitting for a few months starting it every 2 weeks or so until one day i went to start it and it wont start. it'll crank and sound as if it will just about start but then doesn't. i have since checked for spark, replaced the spark plugs/wires, replaces the rotor and cap, fuel pump sounds to be working, emergency shut off is not triggered and i just recently hooked up a OBD1 computer to it giving me error code 31 which i fixed by replacing the EGR valve. now i get no error codes and i am stumped to what might be causing this, any ideas?