car runs great for 15 mins everytime then no spark for 2 to 3 hours then runs

Without testing the car when it is doing it I would guess it is the distributor failing.

It could be many things, unfortunately and without experiencing the problem first hand or being able to do some basic diagnostic tests its hard to say. My guess is that the sensors in the distributor are failing with heat but you would need an oscilloscope to look at the out put pattern (an ac voltage) when the engine is running and then when it fails. The computer for fuel injection/ignition is pretty bullet proof not many problems but basic diagnostic tests need to be done before jumping to conclusions one part or another has failed.Autozone have some popular workshop manuals for free on line once you register (for free) on their website http://bit.ly/autozone_repair_info. There is a company that independent auto repair shops get their information from, this same information is available inexpensively for people that work on their own cars.. The information is year make and model specific, covering repair procedures, torque specifications, fluid capacities and specifications, service bulletins, component locations, wiring diagrams ect.... Alldata is very easy to navigate http://bit.ly/AllData_Repair_Manuals_Online