I am glad that Nissan no longer uses this V6 engine when they introduced the 2005 model. My engine problems began at 65 to 70k miles. I had to replace the Knock sensor that is located deep inside the block. The dealer wanted $1200 to replace; I used a non-dealer where the cost to repair in the book understates the labor hours. The timing belt won't last for 105K miles; they now recommend every 60k that costs another several hundred dollars. Thank god my exhaust manifolds have held up even though my dealer said they needed to be replaced for $1200 (other mechanics said they were ok.) Nissan uses a "plastic" bolt on the ac compressor sprocket. Mine eventually "popped" off.
I am using this space for more engine complaints: This sprocket also holds the belt for the radiator fan. I had to replace the water pump. If the water pump is to be replaced, go ahead and have the timing belt replaced; it will save you money.
The engine developed a metallic ringing noise when you accelerated. Adding a washer to tighten the bolt on the AC sprocket eliminated this noise. I have a noise eminating from the dash area when you want to accelerate uphill. You can hear the AC compressor coming on and off now. Back to the shop!