I have this ticking noise when my car is idling and this started when the car had about 15,000 miles on it. It was only about a year old and I don't drive the car alot because I work very close to home. I had this checked by a mechanic and he said that there was nothing wrong with it, but that sometimes that particular brand of engine will do that. This sounds weird to me because I have never heard of this before. My temperature gauge will also go up when I am idling and will get noisier when this is happening. This started around the same time. I have not had any other issues with the car besides the O2 sensor going out and my check engine light does not come on even though the car is making this noise and idling.