Hey all, I am trying to find out why my idle is jumping all over the place when in park and when im stopped at a light. I have ran every test for code 48 except road speed transducer test but everything is in test range. I have a light tapping noise also which some think to be lifters and others valve job. I just had the heads shaved for fiber gasket. I replaced a few lifters but none looked worn. could it be the valves not closing all the way like if I needed a valve job? maybe broken seats or whatnot? any help would be awsome, I am trying to make it to yellowstone this summer and I would be so cool ( atleast in my head ) if I got to bring my rangie!