Thank you for the response and this idea. I was able to pull down the carpet at the top of the driver's footwell and it seems I don't have the same issue. Mine looks more like a sprayed-on foam and is not deteriorating. I was also able to pull aside the carpet at the passenger door frame and the foam there was also not deteriorating. I smelled the foam in both places and it didn't seem to be the source of the smell. I suppose this is a good thing, but leaves me still unsure of what it could be.99TurboBrick wrote: 23 Aug 2026, 14:00 I reached up deep into the driver's footwell, where it is exposed, and found that the underlayment had broken down to the point where pieces of it would easily be broken off. The stuff just crumbles in your hands.
I think I'll continue deep cleaning every surface and try spraying cleaner into the vents as you mentioned. Is there a spray that's made for this specifically? At some point, I'll try actually removing the carpet to see if there's mildew from the past water issue.
Thank you Matthew. This actually crossed my mind as I was sniffing the underlayment. Thankfully, it wasn't biodegrading but it's good to take precautions.matthew1 wrote: 23 Aug 2026, 15:28 Some thoughts: good work on narrowing it down. You can test by putting some in a small container and testing the smell in isolation. BUT: wear a mask at the very least... better, a respirator. I'm pretty sure Biodegradable does not equal Non Carcinogenic. And take precautions when tearing it out, especially.