My 1998 Firebird with an LS1 will only start half the time?

The engine will always turn over but it acts like it isn't getting fuel or spark half the time, intermittent start. When it starts it runs great. The security light isn't on and there is no check engine light on. I hooked it up to a friends computer and no codes showed up. I can hear the fuel pump when I turn the key. I'm not sure what to do, any Ideas?