Tuesday we got in the car and it stunk. so. bad. There was quite a bit of debate about what it could be and the kids decided it was Little’s boots which were laying in the floorboard.
Wednesday we got in the car and it was rank. We rolled the windows down and discussed the fact that the smell was a little bit like wet carpet or mowed grass that was rotting.
Today we got in the car and I needed to find the pump to put air in my tire. It wasn’t where I left it so I thought it might be in the trunk. As I went to look I commented on the fact that the horrible smell in the van now resembled the smell of asparagus. When I opened the trunk I found the air pump AND a grocery bag from our grocery run on Monday. In that bag? A melted and now rotting bag of broccoli.
I just went out to the van and it smells great.
thebluehutch.com 
When Anthony was in high school he had his own Honda Civic. One day he came to me and said his car really smelled awful and he could not figure out why. He asked me to look at his car. I opened the car doors and sure enough it was a rotting rancid smell. Awful. I thought maybe a rat or even a cat had gotten into the engine bay and died or something. However after a considerable tome of investigation we eventually found in his trunk a Tupperware container of corned beef hash he had taken from the refrigerator as lunch a week before had been forgotten and decayed in his trunk in the Florida heat. That I was a smell I will never forget.
This is GREAT.
YUCK!!! So glad you figured it out! My worst was a gallon of spilled milk that heated up in the back of the van.
I did the gallon of milk thing-in my husbands car once. We got it professionally but it never fully recovered!