I have a 2006 Chevy Cobalt… I can smell gasoline ONLY when I turn the heater or a/c on. I have taken the car to TWO different auto shops and no one knows WHAT is causing this. The check engine light came on recently after a radiator flush and the first auto shop said it was a thermostat switch and bring it back the next day. I was leery of this and went to the second auto shop who told me they never heard of a thermostat switch and to bring it back whenever the check engine light comes on again. Meantime, I will not turn on the heat or air because the gas smell gives me a headache.
One of the areas to look at are the fuel injector O-rings. These are what seal the fuel injectors between the fuel rail and the intake manifold. If the slightest amount of gasoline leaks from these O-rings and lands on a hot engine component it can cause a strong gasoline odor.
You might not see an injector O-ring leak at a certain time. But what you want to look for are witness stains around a fuel injector where it’s leaked in the past.
When you turn on the heater or AC, some fresh air is usually drawn into the passenger compartment. If you look at the hood, near the windshield, you’ll likely see the vents where the air enters the heating/AC system. Any gas fumes under the hood can easily enter the passenger compartment through those vents, esp when the heater or AC fan is pulling air in. A very tiny amount of gasoline can make a big stink. It’s a safety issue though, so you should get it looked at asap. Maybe keep a fire extinguisher with you in the car until it’s fixed.