1989 Mercury Marquis Engine will and fire for about 8 cyl a

I have a 302 that lost power out on the road, at a light it jumped and bucked when I gave it some gas and at a gas station it wound not start. I replaced the plugs, cap, roter, TIF and the stator. The plug wires check OK. The coil gives a very good spark. I browered a computer and hooked it up, but I still have the same problem. I checked the EGR valve and it is not leaking. I also pluged the EGR hose, I still have the same problem. The fuel pressure is good at 39 lbs. When I try starting the engine it will fire for a few cyl and quit with what could be a plug firing too soon. The starter will stop cranking due to the early plug firing. The starter is fine and the engine will crank OK with the coil wire unhooked. I am at a loss, what do I look at next?