I'd guess a stripped cam brg mounting bolt.

Go through them and check the re-torque. I could just be a piece of trash in the lifter... If you can use your stethscope and tell which cylinder- then you could only re-torque those 4. If they won't hold a torque- buy a repair insert.

I didn't even know Autozone had distributor rotors and caps for benzs. I'd stick with Bosch and they are not really expensive.


Micheal