Ford Ignition issues?

1985 Ford LTD Crown Vic. Injected 2bbl 302 V8. This car has served me well for over a year. Engine cranks and will occasionally fire right up and drive great. Lately it will just die suddenly at speed or in traffic, and either start again or not. Mostly not. Also when turned off to go into a store, get gas, etc, I come out to have it not start again. Sometimes sitting for an hour or so will let it fire right up, but not today. Three hours of off and on attempts, and had to tow her home. So I replaced the ignition coil, but it still wont start. It appears to be getting fuel, cranks strong, starts right up sometimes, and ocassionally even gets me from point A to point B issue free. What would be the cause of this? I've had many cars and have never had symptoms like this. What would cause a vehicle to run fine then either just die or not even re-start or start. Thanks for any help, Steve