Lifter or Wrist pin
 

Will a w124 engine miss if a lifter collapses and if there is no miss, could it be a bad wrist pin?

a loose wrist pin would make noise under decelleration, i think, and would not make it miss unless very very loose, and then it might actually hit something like a valve.

if the valve adjuster collapsed completely it might miss, if it were off enough. i don't know the answer, but theoretcially it might.

tom w

a loose wrist pin would make noise under decelleration, i think, and would not make it miss unless very very loose, and then it might actually hit something like a valve. the wrist pin if that is it can tick with little or no ill effect on a motor for many miles, i seem to remember. a wrist pin seems unlikely on the robust benz lower end.

if the valve adjuster collapsed completely it might miss, if it were off enough. i don't know the answer, but theoretcially it might.

tom w

Generally speaking - don't know why a Merc would be different. Wrist pin = tick, at least until it gets very close to going and should get louder under load or when backing off. A lifter will just hammer, scare the hell out of you, and may seem like it's missing.
If you oil is old, I'd first pour in and additive to see if the lifter frees up, and then switch to syn.