I have an 09 G37Xs AT that seems to run, and has always run perfectly. The other day at idle it sounds like a bit of a rattle, like an AC compressor or PS pump or something. Car has always been dealer maintained. I notice no difference in running or steering etc and when I hit the AC compressor it doesnt change it. Opening the hood it sounds like its coming from the passenger side of the motor. Couldnt really spend time to figure out if its the motor itself or an accessory, since it was 3 degrees out and windy.

If you have any thoughts let me know! Oh, and Im about 500 over for an oil change but level is fine and oil is still clean.

Bob

500 over on oil won't cause a rattle.

Best thing to do is get a really long screwdriver and put the handle to your ear, and as you touch it to things in the engine bay, it transfers the sound up the shaft to your ear. Poor man's mechanic's stethoscope.

I actually started to do that but it was 3 degrees out
When I bring it in to the dealer for an oil change Ill mention it but I don't trust them at all. They wouldn't find a problem if the entire car was on fire.
Ill let you know what I / they find.

Yeah, I've fallen off the dealer bandwagon. Only time they get to see anything of mine is when it's still under warranty. And I don't blame you about the 3 degrees. It got that low here last year, so I know how it is.

I believe I have the same issue on my 08 G35xS. Started couple months ago & I narrowed it down to the passage side exhaust down pipe (cat converter). I think it's just the heat shield. Didn't have time to work on it yet.

Thats actually what my dealer diagnosed it as. $1700 to fix so that wont happen. I guess Ill never know

The heat shield is, like, three bolts per catalytic converter. Jack the car up and tighten them.

On mine it was the element inside, not the heat shield.

Then it's time to change it, not leave it. If the cone is breaking up internally it can actually get ingested into the cylinders. Strange as it sounds it's happened.

I ant even imagine how that would happen. Air doesnt flow that way. Yes, it should be changed, but I cant imagine thats the reason wy

Back pressure during the stroke cycle, or maybe an off-gas situation, has been shown to pull up broken fragments of cone. There have been quite a few reports on it over the years. It's weird and not something I would expect but it is a possibility.

You could get a warranty replacement if it turns out to be the catalytic converter. I had a rattling noise from it and dealer replaced it under warranty. Emission parts are 8 years.