I wanted to thank whomever started this thread years ago as well as to everyone who had posted over the years. This thread has helped me tremendously, and I joined this forum just to be able to express this gratitude. After my 2004 CRV with 225,000 miles bit the dust in a 3-car accident last June, I bought a used 2014 CRV with 36k on it. Once it reached in the early 40k range, I started getting the random start-up grinding noise and it started causing me some concern. As you all well know, it wouldn't occur every time, and when it did it lasted for a second or two. Always (when it did) on the first start-up in the morning. I would go two weeks without the noise, then it would do it again.
I recorded the noise on the cell phone and played it for a local dealership, and they said that they would need to have the car in person and hear it for themselves before they could properly diagnose it. Leaving my car there for who knows how long would have been a major inconvenience. I did some research online and found this forum with this particular thread of 120+ pages of comments and analysis. Then the car started to make the noise on an evening start-up two or three times over the course of a few weeks.
I emailed the mechanic at the dealership, with a link and the summary information from this thread and told him I was bringing the car in to leave there for diagnosis and repair (pointing out the VTC Actuator issue). I had to rent a car to get back and forth to work while they had my CRV. The following morning they heard the noise, and the morning after that they called me and said they replaced the VTC Actuator and it was ready to go. No charge as it was under the power train warranty (was well under 60k, actually was under 48k).
So far, the first two mornings after the replacement (and, yes, they did replace it with the newer Part# 14310-R5A-305), and I have not heard the grinding noise upon start-up. I'll feel more secure about it if I go through the rest of February without hearing that noise, but so far so good.
So, once again, THANK YOU ALL for this invaluable forum thread that helped to get to the source of the problem with a quick repair at no charge (except for the rental car). All the best!