My 25k mile 2011 2.3L Ranger has always made a mild knocking sound while idling. It appears to be coming from the area of the first catalytic converter. Kinda sound like something you would hear on a diesel engine. I’ve taken it to the dealer several times and they always say there is nothing wrong with it. It is still under extended warranty so I made the dealer replace both catalytic converters. Still sounds the same. They also verified the are no manifold or exhaust leaks.

Anyone have any ideas?

 

Do you here it more In gear(automatic) or in neutral(Park), or doesn't it matter?

 

Doesn’t matter.