Hi guys. I have a 2007 4.7 v8 grand Cherokee that has been giving me a big issue. I hooked my jeep up to a scan tool and I get the piston misfire code. When cold my engine runs fine but once it gets hot it starts to idle really rough. Sometimes is goes down to 4-500 rpm and eventually stalls. Also I'll be randomly driving and my jeep starts to shutter very violently and I lose power and the engine light will flicker on and off and eventually stay solid.. I just got the engine replaced an I have about 5,000 on the new engine and 94000 on everything else. I know it's not the spark plugs, and I checked for a vaccume leak and it doesn't seem to have one. Also somtimes when I start my car there is a loud metal clinking sound. It's kind of hard to describe but it sounds like there's a piece of metal in the exhaust or somthing. please if anyone could help of have had this problem before please help.