2002 Ford Taurus comp. Problem

2002 Ford Taurus

Was told my # 2 cyl. Only has 50% comp. And will need to be rebuilt. Was running rough prior to replacing plugs, wires and coil pak. But did not correct problem and had car looked at and was told a rebuild was needed or new engine. Car was running good and no knocks with great exceleration. Would this be a fact. Had car looked at because after running for about a few minutes it stopped and would not start but just turned over and popped a few times without starting. Any advice, thanks