Engine noise at start up

[markmatu]

I just purchased a 1997 Pontiac Grand Am for my son ($3,400). While it is in great shape interior and exterior, it does run rough at start-up. The engine runs loud and there appears to be a great deal of engine noise, as if it is running fast. Is this typical, or can I expect to replace the engine really soon?

Anyone ever have these symptoms?

[Slade901]

Is it a loud knocking noise and is this noise even evident while at IDLE?

A vehicle which was used by someone I know was driving the vehicle and not even doing a regular oil change and developed a loud engine knock (I've fixed it adding 1 quart of Gunk Motor Oil Flush to the existing oil and start the engine for 5 minutes and turned the engine off and drained the whole oil and we put 5W30 oil in it and told the owner of the vehicle to change the oil after 1,000 miles to 10W30 and follow the 3,000 oil change maintenance).

Another engine knock I encountered after we bought a used truck. During test drive, it was fine and no knocking noise but after driving it home after purchasing it, engine knock developed and it is evident while at IDLE.
I've followed the same procedure as above by just adding 1 quart of Gunk Motor Oil Flush and put 5W30 but that did not fix the problem. I was told that the engine was dead and need replacement. I went and replaced the oil pump and oil pump filter/strainer. Put 5W30 oil and this time the engine knock was gone. Replaced the 5W30 oil after 1,000 to 10W30 and followed regular 3,000 oil change maintenance and the engine knock has not come back (knock on wood).