Your mechanic doesn't know what he's talking about. Yes, chains stretch over time, but there is a tensioner that prevents it from causing any problems.
Yes. me too i think that's funny diagnosis. that's why I want to check the length of my chain, and compare these to the correct length. Mechanic says the tensioner is extremely extended and the chain needs to be replaced.
In Europe is a very unusual engine. Pathfinders are sold here only with a diesel engine. Here it is difficult to find a mechanic who knows about VQ40De