need to know what to do engine knock when normal temp & oil pressure idle speed goes below 600 knock hard knock on top end hard sounds like lifter going flat. what can be done to stop this & can it cause engine failure?

 

I can't give you an answer but i can sympathize. My 02 has been doing it for a long time. No rhyme or reason though. Sometimes it knocks, sometimes doesn't. I can't figure out why or when, i just watch the temp and oil pressure and level, and hope for the best. Good luck, i think there are many out there doing this. Is it a 5.4?