
I have a 2011. 80K miles. Started hearing the noise around 77-78K or so, but only a few times when it was really cold outside. Timing chain. The noise was exactly as described on this forum.
I brought it home to discuss the options with my wife - trade or fix. As I was about to take it back for service, the check engine light came on, and it wouldnt rev past ~1500 RPMs. Had it towed to the shop. Service adviser said that pieces of the chain had started to come off. Thankfully, no extra damage was done.
Has been a fantastic vehicle otherwise. Bought it used in late 2012 with ~30K miles on it.
One thing he did tell me was in the motors where the timing chain has failed it can fill the catalytic converters full of fuel causing them to prematurely fail later on. He just covered an out of warranty converter for an 11 qx that they replaced the timing chain on several months back under warranty. The vehicle was out of warranty when the converter failed and Infiniti tried to refuse paying for it saying it was unrelated