I have a 2010 Legacy 2.5i with 48k miles. I like the car except for one thing. It sounds like marbles are in the engine when idling. I was thinking it was a belt tensioner, but you would hear the belt squeak when accelerating.
Sometimes the car makes a slight, brief (1 second) "crackling" noise when accelerating under partial load (<20 mph).
At normal driving speeds, the noise goes away.
This is kind of weird. Does the car need a valve adjustment or something else?
The car does this when warm to hot rather than cold.