I Am having a proble with my 1993 cadillac seville 4.9 L V8 engine. It trembles when I Accelerate and when At idle. I tried to put in a new egnition coil distributor cap spark plug wires and spark plugs. I was also informed that the previous owner did not give it an oi change for about 60,000 miles and in might be a worn out part like the crankshaft for example. Pls help.