My car is getting a tap out of the drivers side valve cover, and the computer is sensing knocks and retarding the timing. I readjusted the rocker arms and everything felt good, but the noise is still there and timing is still getting retarded. How can I diagnose if I have a bad lifter with out taking everything apart. Or does this sound like a problem in the head? Thanks in advance for any help.

 

sounds like a bad lifter and you better not run the car anymore and pray it didn't eat the cam...unless you want that...

 

Pull the valve cover and start the engine (I know this is a little messy) Try to isolate the lifter by listening through a piece of hose or whatever way you prefer. Tighten the rocker arm nut slightly (1/2 turn or so) and see if noise goes away. If a lifter is bad usually the tap will go away for a second and then slowly return (about as long as it takes you to straighten back up after bending over in the engine bay)...Good luck...
--Alan