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So my 2000 Honda Civic has a gas smell coming through the vents when I am idling at stop lights on hot days. It's not every stop light, but happens occasionally. I popped the hood and couldn't smell anything under there, but the car smelled when I got back in it. I think it's coming from underneath the driver's side and coming up into the vents that way which is why I don't smell it while driving, but I'm not sure. Wondering if it has something to do with running the a/c since I do on hot days. Haven't noticed any puddles under the car when I get in, but it's really hot here so a drop of gas would evaporate almost instantaneously if there is a leak. I haven't had any services recently. Got an emissions test done in colorado 2 months ago before heading out to nevada, and it passed. No check engine light. I tried sitting in the car in the parking lot with it on and the a/c running and then shutting off the a/c and keeping the fans on. Checked under the hood, but didn't see anything leaking and I didn't smell anything, checked under the car, no drips or puddles. Seems like I have to drive it around for a little bit before the smell starts. The day (about a week ago) it started I think I hit like 7 red lights in a row and it was like 110 degrees. Any ideas? I plan on getting a fire extinguisher just in case...hoping it's just a little extra fuel in the lines causing the smell somehow and not a leak

 
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you can close this thread if you want, I talked to someone and he explained what the issue was pretty quickly. Hasn't been nearly as hot and the problem went away.

 
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What did he explain? Mine did the same thing recently. Turned out to be unburned fuel in the exhaust because of an occasional misfire due to a failing coil. If you start having hard starts, have a look at your ignition.

 
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I'm interested too in what high temperatures have to do with gas smell.

 
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more than likely an evap system leak

 
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Any mechanical downside to that? Worse mileage or anything?

 
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Well. It's not safe for 1. For 2 yes it would affect mileage if your evaporating gas on a regular basis. Safety is the number 1 priority though.

 
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gas vapor is flammable and you have a hot engine next to it.

 
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It's pretty easy for the OP to inspect the evap system isn't it? Mine sits right under the fuel filter. How would he go about the inspection?

 
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evap system is very complicated and has lines running around the engine bay as well as from the bay to the fuel tank. could be a leaking line or a bad valve or canister. its difficult to pin point the problem. could also be coming from under the rear seat cushion if the fuel pump cover is leaking.

 
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he said that the fuel pressure regulator (can't remember what he called it) under the car is designed to release vapors at a certain rate, but with the starting and stopping at all the lights and the high temperature (pressure goes up at higher temps bc gas expands) that there was probably too much pressure in it and it was release a little more than usual.

He also said that if it were a leak I would smell it all of the time, and if it were near the engine I would smell it all the time too because it would come through the vents even while on the highway. So most likely under the car or towards the back. It hasn't happened again since I posted the message, but it hasn't been nearly as hot and I drive on a road with far fewer lights.

 
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thats good i guess, but its still a problem. the whole point of the evap system is to keep fuel vapor from being released under any conditions.