When starting 'er up with a cold engine, seems "noisy" and a bit rough, then after a minute or so - smooths out and sounds "normal"... It's been there since new but I only really noticed lately after starting in the morning and listening.

 

My 2009 G37xS does the exact same thing. I was thinking about asking the dealer about it during my next oil change, but I am pretty sure it is normal...

 

it's normal.

 

Looks like the consensus is that clattering sound on cold start is normal. But does anyone know why?

 

They all sound raspy when you cold start them. It is completely normal. It is caused by the high idle speed needed to keep the engine running after a cold start and because its running really rich to try and worm up as fast as possible.

 

My 07 G35 didn't sound like that at start up. It may be normal for the VQ 3.7 engine.

 

Certainly not a smooth start to the day, when started in the morning. I guess it is normal, though; there is another thread on this. Having it sound like an old John Deere tractor early in the morning can at least bring back memories for me of growing up on a farm :-)

 

Should be normal bc of the cold start. It's usually like that on most cars..

 

I have a brand new 2010 and it does the exact same thing. Really throaty sounding on a cold start, always goes away after a minute or two.

 

Mine too.....brand new also. These engines are forced to run lean at start up to minimize pollution...makes them run a little rough at first. My 04 TL was much the same way.

 

A while back, I was shopping for exhausts for my G37 and came across this video. Great sounding exhaust but it's very noisy at startup and then quiets down. You can't really hear the engine roughness but it does exhibit the same quiet-down effect that I've experienced with mine and that others have described.

Interestingly enough, I never experience this issue unless the car has sat overnight. I can come home, leave the car sit for 2-3 hours, restart it and it's completely smooth as silk.

I suspect that on a cold start, the metals inside the motor haven't expanded all the way and once they're warm, they expand in size ever so slightly...I'm talking in micro-level increments but engine tolerances are so tight these days that it could be the cause of the noise.

I have heard other guesses that it has something to due with the VQ37's VVEL system. I did not experience this issue on my VQ35. It would be interesting to see if this issue occurs with other engines that have VVEL, such as the M56 to see if similar issues occur.

Any M56 owners that are able to chime in?

 

I actually prefer the warm-up sound.

 

yeah my car is noisy too. But like other folks have said, it quiet down after little while.

 

Mine does the same thing, also has a ticking noise when sitting idle....

 

Just got my G37 yesterday. The vehicle still had all of shipping wrap on it and when I started it before negotiations it did the same thing. This morning in Houston it was 61 when i started up and it did the same thing. Within a minute all was quiet.