Hi, it's my first time posting here and was wondering if anyone could help me out. About more than a week ago, I noticed this rattling noise on my 2011 G37X Sedan . Every time I accelerate from 0-3 rpms I hear this rattling by the driver side of the car. Plus you can hear it more when it goes from 2 rpms back to 0. I'll post a video up so you can a better understand of what I'm taking about. I saw this other youtube video as well with same car and had a similar sound, apparently it was a bad catalytic converter. Do you guys think this might be the issue? Any help would be appreciated!!! Thank You!!

 

 

where you live? ill put my money on some place with salt!!
I have been battling this same issue myself since i bought my car last year.(2011 g37x)
My knucles are actually still freezing at time of typing this from putting on yet another hose clamp this morning around yet abother rusted heat shield.

Might not be your problem but could be:
Rusty heat shields!!
Get under your car (when its cold) and put your hand on around the cat and exhaust. Are the heat shield on nice and tight and clean or are they rusty pieces of **** with every clamp bolt rusted off. Cause this was the case with mine and causing the same sound your describing.
If you have acess to lift that would be the best option really give yourself a good look and easy access to what needs to be done. luckily a buddy of mine has a lift so we replaced all the rusty clamps with hose clamps in one shot. Tho as you can see earlier in my post I must have missed one, sucks sucks doing it on your back in december in boston.

tldr: probablly rust heat shield rattling against cat and or exhaust

 

I'm from New Jersey and I just got the car back at the end of September. I'll have to check the heat shields cause that might be the issue like you were saying. Did your car make that same noise as well when accelerating and when it decelerated? I just hope this isn't a serious issue and want to solve it already cause I don't like the way it sounds. I'm gonna check later today and ill keep you updated and see if can post a better pic of the exhaust and cat

 

 

Just curious why do you say x model? Is it solely because of the assumption that most x models are going to be sold and used where salt and snow is seen. Or is there another reason?

 

 

I'll tell you this much, I've got an X model, and of course it also has the same noise coming from it! Granted, it only seems to happen from a cold start... I've yet to crawl under the car as it's too cold to do so in Toronto, but once I do I'm pretty positive that I'm going to have a rattling heat shield. (I've already had to replace some clips on heat shields on the driver AND passenger side of the car, because they were completely rusted through! The sound was horrendous!!)

I'm sure I'll be back here and let you know once I get my hands dirty

 

Sorry for taking long to get back to you guy, I've been a little busy lately. I ended up checking one more time underneath my car to see if any heat shields were loose but didn't find anything so it had to of been the catalytic converters. Today, I decided to take the car to the dealership just to confirm that it's the catalytic converters which they confirmed it was. They also said that I need to replace the Y pipe cause the noise could be introduced again even they were to switch both cat converters out which they quoted to replace for $1644 but that's just way too much. Also I was told I needed a new fuel dampener cause it was making a small noise as well and they quoted me another $460 to replace that. The good news is that they will replace both cat converters cause it has the emissions warranty that covers up to 8 years or 80k miles and mine just hit 75k today. I had plan to get a whole new exhaust system in future but now that I need a Y pipe I might as well just get the whole thing. Do you guys have an suggestion or recommend any type of exhaust system or maybe just a Y pipe or should I just go with an OEM Y pipe. Also have any of you replaced your fuel dampener? If so, how was the installation process?