A good tip, one that truckers have been using for a while, is to add ground coffee mix directly on the spot and leave them there for a week or so. The reason for that is that coffee contains a series of oils that absorb odors. There is no need for expensive coffee, even the cheapest brand will do and it won't even leave a stain on the carpet, so there is no danger.
Another odor-neutralizing substance is baking soda, and lots of it too. Sprinkle on the spot and leave overnight. The next day, brush it off and then you can vacuum the rest. The smell should be gone, and you're free to drive around all day without feeling sick to your stomach.