93' Cougar - Loud Knock?

I can start my car just fine. But after my car warms up, it starts a loud knocking sound. At low speeds it starts to stop if i push on the gas hard, but it comes back after it shifts. After driving it for a while, i go to park and it dies. Sometimes it starts right up afterwords, sometimes it takes 10-15 minutes. The oil was just changed and checked before I posted here. Also, my coolant is full, all fluids are fine. It hasnt died on me on the road driving, only when I come to a stop at stoplights. I'm not a complete newbie about cars, but i'm not a certified mechanic. Can anyone help? :banghead:

Are you losing oil pressure this will cause a bad knock. Maybe a plugged strainer. A bad thrust bearing will cause a knock. Watch the harmonic pulley does it move back and forth when running.
Be much more definate describing the sound.