I would not assume the timing chain is the problem. Especially if the warm/cold weather is not a factor for timing chains, when they rattle - they rattle all the time.. Check the turbo shield cover. That is the main problem when experiencing rattle on N13 engine.
It is all explained nicely on the following thread. Cheers mate
https://f20.1addicts.com/forums/show....php?t=1657132