2001 Dodge Intrepid

If the connecting rod on the piston(s) is loosening up because of a bearing and oil pressure problem it sounds like a knocking sound. And low octane fuel causes the piston to hit the cylinder and make a knocking sound. They call that pre-ignition or fuel pinging and knocking. Sometimes it is hard to tell them apart. If its running too hot it will pre-ignite the fuel also.