I've been meaning to ask this - and yes, I have searched....

When I start my car (cold start), it is somewhat louder than normal for the first @15-30 seconds. Unsure if it is intake or exhaust - guessing exhaust.

What is that?

 

I've had similar noise from my 09 sedan since the day I bought it. Kind of sounds like an empty coffee can with nuts and bolts in it for about 30 seconds, give or take 10 sec., after which it quiets down to a point I can barely hear it running. The engine runs like a real champ and the engine hasn't been any the worse for the noise. I just don't let it bother me any more.

 

I don't know this to be 100% accurate, but I heard somewhere it's part of the start up sequence that helps get the engine up to operating temp as quickly as possible. Supposedly the fuel and ignition is different for that time period...

 

Yeah - not a bother. To me - almost sounds like it has an aggressive exhaust on it - for about 30 seconds. Then - as you said - it simply quiets down and sounds 'normal'.

I just find it interesting...wondering what the heck (or why) it does that...

 

For the first 30 seconds I have a cbe.
Then I don't. LOL
MINE DOES THE SAME THING.

 

Mine does the same thing. I thought the engine went from rich to lean.

 

Interesting. I just thought it was the cats needing to heat up.

 

Coffee can sound mentioned earlier best description, thats exactly what it sounds like. Give it about 15 seconds and I noticed the RPM's go from 1500 down to about 900. And continues to decrease till its a quiet idle.

 

...my favorite part of the morning!

 

The best part of waking up....

 

When I first start my 2010 G37 it sounds like s**t. I also have a 2011 Sante Fe 3.5, 6 cylinder. When it starts up it also sounds terrible, it's as if there is no oil in the engine. I guess I'm just use to the sound of a V8.

 

My Tundra with a 5.7L would sound like a diesel truck on startup until it was warmed up, almost sounded like an exhaust leak. Noticed similar terrible sound from the 335i right at startup, same thing from the a4. My G37 does it as well, but stops after a few seconds. It's just a modern car thing it seems now.

It's this stupid emissions stuff to cut back on the amount of pollutants when it first starts up. My truck had this air injection system that sounded like a vacuum cleaner for 30 seconds where it would blow air into the exhaust. Completely pointless for 30 seconds of "clean air". They were having some major issues with them and Toyota wanted almost $4k to replace the system, when it broke you'd go into limp mode. They since have had to extend the warranty to 10 years 120k miles. Still ridiculous IMO. With the new efficiency/pollutant regulations I can only see this getting worse and more complicated.

 

yup, coffee sound indeed

 

It's a VVEL thing. I don't think the pre 09's sound like it.

While revving a cold engine is not good...I've done a small test. When the car starts up fully cold it make this diesel type sound within 4-5 seconds of starting. Now...if i just slightly tap the gas pedal (rpms will jump to 2K-2.5K) the engine gets super smooth as if it was fully warmed. After a few seconds the rpm's will come back down to the cold idle. As they are settling the sound comes back as the VVEL is probably re-adjusting.

I'm pretty sure the VQ35HR don't do this but the VQ37VHR do.

 

Yes - I can tell you my '06 350 (w/DE 3.5ltr) did not do this. Nor did my '09 Murano. Hence the reason I asked