I just picked up a 03 G35 sedan from a small lot. 59000 mile, clean and pretty much regular daily driving wear. The engine has a clicking or ticking knock noise in the engine. One of my friend said it is possibly lifters, others said bent valve. The mechanic at the lot said all it needed was a tune up, oil and spark plug change and it would go away....It hasnt after 700 miles. the car still has their warranty so im getting it fixed through them. Here is a Youtube video of the noise.....thanks for your help!!!!

 

if you haven't fixed it maybe try putting some AMSOil PI http://www.amsoil.com/storefront/api.aspx, just locate a dealer its like $10-12, i remember the guy saying it can help get rid of the engine knocking. Its worth a shot, i used it in my coupe and loved it, it works.

 

Had a similar problem was think in valves but just wanted fresh oil put some royal purple 10/30 and went away mine never got that loud tho

 

i had the same issue with my previous g35 and a oil change took care of it, never heard it again.