hi guys my 01 has developed a rattle it almost sounds like it is around the injection pump. it has surged in the past but i started using diesel kleen every other fill up an it has not surged since. but i have noticed the engine change tone while it is idling but i cant see a change on the tach. it just has a different sound to it. could this be the fuel pressure regulator? also is the fuel pressure regulator and the fuel pressure regulator valve the same thing??? thanks oh ya the truck has 178k on it now

mine was rattling because the tensior pully was bad.

nope ive taken the belt off and its still there any more ideas?????