I own a g35 05 sedan and theres this noise more like a rattle that is driving me nuts. It only happens at acceleration about 2 rpm's than it goes away and I notice it better if you put it on D and set the breaks and accelerate, you can definitely hear it clearly and again at 2 rpm, even the dealer can give me a minimal answer to what it can be . Can anyone help thanks!! Ive try the following (Change the compressor rod bushings, mass air flow sensor and various Diagnostic @ infinity dealer!! I always do the oil change @ 4k miles and use mobile 1 full synthetic oil plus premium gasoline).

 

It could be your exhaust heat shield is loose or one of your cats is going out and it would rattle because the honey comb inside is breaking up but if it was one of the cats it would have a higher heat temperature than the other one.

 

It sounds like ur pinging could be bad gas. Or even some gs ping a little just because and the dealer says its normal

 

Well as for the pinging, I don't think so cause Ive put my car on a lift and put it on D, press the breaks and accelerate to see if I can notice the sound better as if when the car is on the ground or with load and there was no rattle at all.
I'm just very frustrated, but if the problem is what Nismo thinks it might be how can I fixed it or get it checked?

 

Heat shield probably. Check them for broken welds. You can usually bend them around a bit so they won't rattle

 

Oh by the way forgot to mention that the noise sound the it's coming from underneath the front kind of like where the engine sits.

 

I know this may sound like it doesn't make any sense,but if someone has put belts on your car recently and they are too tight it will cause a bottom end knocking sound due to the stress on the crank,try loosening the belts and see if the noise goes away...hope this helps, Jason

 

had the same problem, the sound was from a loose heat shield. instead of bending it i used a hose clamp to hold the shield together.

 

Hey I've got this same problem too. Do you think you could post a pic of where exactly you clamped the heat shield?