hi all im pretty new to cady's its my first one, well here is the prob, car runs fine and starts fine but some times it dont want to start it turns over but no start its only after driving for a long time, prob 2 is a knocking under the valve cover, it stoped when i added oil but it comes back now and again and that is when it dont want to start, prob 3 is when turning it jerks, at one point in turns if feels like its sticking then jerk it turns, any help would be great i love this car...

87 sedan deville
4.1 alum block v8 stainless sleavs
digital electronic fuel injection
power everything