I have a 2005 Dodge Ram 1500 4.7L magnum, when in park and even sometimes in drive or any other gear for that matter, the idle rpm is very erratic. It raises and lowers from about 500 to 1200 rpm. The only fault code is bad knock sensor. I thought the knock sensor was only active during acceleration, don't really see this being the problem. I replaced the map sensor but still have the problem. Any Ideas???

 

This is simple stuff but spark plugs ok? Fuel rails getting the right pressure?