One problem related to engine knocking noise has been reported for the 2006 Infiniti G35. The most recently reported issues are listed below.
At ~7,900mi, I took my G35 coupe 6mt to Infiniti dealership when I started hearing a knocking noise and noticed that the "check engine" light would come up every few times a week. I was called in 4 more times after that (every 1,000mi) specifically for oil-level testing. The dealership received an approval to replace the engine, and at 14,500mi, after just about 6 months, I drove out with a new one (10102-ac7m9). I was told to go easy for the initial 12-15k. After driving about 1000mi now, I am running low on oil. I just checked it myself. I plan on taking it to the dealership soon to record it formally. But this is not the only problem I am having, the new engine seems to be a lot louder and a bit sluggish too. . Yes. . Definitely not the ride I got used too!!.