For the past 3 summers I have a nasty smell in my kitchen. It lingers all the time. I don't use an air conditioner. In the morning when I get up the entire kitchen smells. I open the doors and windows but the smell remains throughout the summer. When the air goes on, the smell is gone. It disappears when the heat is on. I clean the cabinets, the smell doesn't seem to be coming from under the sink, I cleaned out the refrigerator, (under, inside, around), I cleaned the gas stove. No leaks under the crawl space, sink.
Help

Do you have a dishwasher? That may be the culprit. Too much black gunk gathers around the door and inside that can smell really bad if it isn't cleaned out well enough from time to time. I run chlorox through my dishwasher once in a while (not enough to damage gaskets) and that gets most of it cleaned out but the best bet is to take the door off and clean everything.