Q: Difficulty getting car started

Initially, my car would start, but it was difficult. While driving, it would try to stall at a stop unless placed in neutral. When you pushed the throttle to the floor, the car was sluggish when gaining speed. I replaced the spark plugs, oil, and distributor cap. I also checked out the various systems in the car and made sure that piston one was at top dead center. Now, the car will not star. If we play around with it, we can sometimes get it to start, but it stalls soon thereafter.