my G starting to smell like rotten vegetables in the last month, it only happen when I get back into the car after it sitting for an hour or more. The smell is worst when I get in the morning. The smell goes from the driver seat to the trunk.
What i've done:
- Changed out cabin air filter
- Checked and cleaned the intake part of the HVAC (behind the battery)
- I always kept the interior clean
- Trunk are always clean as well

After searching through some of the threads, my conclusion is either there is mold in the HVAC which I need to get a AC refresher kit or it is really time to replace the CAT since I've been trying to avoid replacing it for almost a year now.
What do you guys think?

 

It could be your catalytic converter going bad, or possibly a leak at your test pipes or headers

If it has a rotten egg smell on cold start, or when you accelerate with the windows down, it is most likely the cats.

 

Then smell is even before I start the car, and once the car started going, the smell just goes away. That means it is possible that the smell can get worst to the point of even having the smell during acceleration?

 

Check your carpet in the footwells of all 4 seats to see if it's wet, might have a clogged sunroof drain getting the carpet wet and making mold.

If it smells like a dead animal you might have a mouse that died in the car somewhere, it's definitely possible for them to eat a hole in the cabin air filter and get into the ductwork then die.

Probably not your cats since that is a distinctive rotten egg fart smell that will NOT be present first thing in the morning before the engine is running.

You should also pull out the ENTIRE trunk, carpet, spare tire, then both those plastic dividers on each side until you get down to the HICAS controller and wiring just to make sure there's not a family of dead mice in the trunk somewhere.

 

If it does turn out to be the clogged sunroof drain (common issue; also be sure the plastic drain line hasn't detached from the nipple), you will want to pull the carpet to dry it out properly. There are wells in the floor pan that are filled with foam blocks to level the floor. Water collects in those wells if you have a sufficiently heavy leak. Just surface drying the carpet won't remove the smell.

 

One thing for sure then is I'm glad I don't have to replace the most expensive part on my car, but looks like I'll need to dig deeper to find where the smell is coming from. So far, the floor is dry. The only thing I remember that had leaking was the passenger side A pillar. Went through a touchless car wash and it leak a little bit at the top of the A pillar trim, but it didn't leak at all during a heavy rain, so far no luck in figure out how water got in there.

 

Get a cheapo borescope camera and look into the duct from the cabin air filter.

 

Never thought of that! and just found out how cheap they are. Going to get one then. And strangely, the smell slowly went away...

 

Makes sense if it is a dead mouse, after the decomposition process has completed there is barely any smell, the only reason you smell dead animals is the bacteria decomposing all the soft parts (bacteria creates gas which is what you smell), once that process has finished then you're left with the dried up remains which has almost no odor. Takes about 2 weeks start to finish but that depends a LOT on the temperature and humidity of the environment and airflow.

 

He said the smell mysteriously went away after he changed his undies. 🤷‍♂️

 

Or something that smelled bad finally broke loose and left the car. But I'll still get a borescope so I can search around the car. Is like there are weird issues that I can't seem to find answers. Such as when I accelerate from complete stop, there are squeaking noise from the both back passengers' roof handle, but doesn't seem like it is the handles itself that making the noise.

 

I'd suspect suspension components wearing causing that squeaking sound to appear to be coming from the ohh **** handle as the sound resonates up through the headliner. Depending on the squeak SHOCKS are pretty notorious for making sounds like that, plus when you accelerate from a stop you get a lot of weight transfer onto the rear shocks. The top mount is right behind the rear seatback and that noise could be resonating up into the headliner.

Fold your rear seat down and reproduce that sound to see if it's more noticeable where it's actually coming from.

 

Had a mouse crawl into the intake and die. It will reek for a bit, then go away. Found it while changing the intake filter.

Also lift the carpet and check the if the under padding is wet. If it's a new smell, it might be wet underneath but dry on the surface. Clogged sunroof drain lines are unfortunately extremely common.

 

Somehow I couldn't find any dead animals, or wet carpet, but the smell went away lol.

 

I found two dead birds today sandwiched between my radiator and AC condenser. I have no clue how they got in there since they would have had to crawl in from the side, but they were there, and they were gooey still... car has been sitting for a couple months over the winter season.