i recently bought my '07 F-150 5.4L with 50k miles and i never noticed until a couple month after that it has a terrible engine knock when it is up to temp. the knock only happens when I'm making a parking lot maneuver. i read once that if i rev it above 1500rpm when making the maneuver it won't knock and it was true. what is causing my knock

 

Mine does the exact same thing, the engine makes a knocking sound when it warms up and the engine is idling or the truck is just barely moving around. It quits when you get moving down the road. I posted on here about it but got no response that I can remeber though. I tried going to 10w40 but it did the same thing so I went back to 10w30. Does anybody have a suggestionas to what this is?