Why won't my car stay running?

My 94 chevy lumina will not stay running. I already changed my fuel filter and my pump is still working fine. I have checked to see if there is arc and two of the wires I checked I got nothing. So now what do I do know, I do know if its a bad spark plug wire or something else that is causing it not to fire. It will start up and run fine then just shut off thats when I checked for spark and got nothing. It only starts once or twice a day and thats all I can get out of it. When it does run it runs really good. Does not make any sounds that a spark plug is missing or not getting enough fuel. It shuts off as if I turned the key off myself. Sorry if little confusing thanks for any help