[Astone22]

2013 n20 with 40k. I smell gas on first start up of the day. Any idea what it could be

[davidr3]

Normal, cold starts always will contain a smell of fumes till your CAT heats up since that's what is the "filter".

^^ this is if it goes away when warm & do you start it up in a garage or something?

[auburnf30x]

To me, this is odd. I have never smelled fuel coming through the HVAC system on cold starting in any car, except for my old truck which has no catalytic converters.

Is it a raw fuel smell? Does your car sound excessively loud on cold start? You’ve got a leak somewhere, question is whether it’s on the fuel delivery or exhaust side.

[Doug Dimmadome]

I've never experienced this either

[Elvisfan]

Originally Posted by davidr3

Normal, cold starts always will contain a smell of fumes till your CAT heats up since that's what is the "filter".

^^ this is if it goes away when warm & do you start it up in a garage or something?

I’m no expert but, this makes no sense to me. What do people with Catless cars do? Cats don’t burn off gas.

[davidr3]

Originally Posted by Elvisfan

I’m no expert but, this makes no sense to me. What do people with Catless cars do? Cats don’t burn off gas.

Catless cars always smell like fuel.. They don't do anything except smell fuel nor did I say cats burn off gas. The precious metals, (typically platinum and rhodium which is why people steal cats) use a redox reaction & this is what filters out the smell and regulates emissions. When the cats get up to operating temp is when they work the best. Hence why cold starts are loud since the car is trying to heat up the cats more rapidly.

[njdangelo]

Originally Posted by davidr3

Catless cars always smell like fuel.. They don't do anything except smell fuel nor did I say cats burn off gas. The precious metals, (typically platinum and rhodium which is why people steal cats) use a redox reaction & this is what filters out the smell and regulates emissions. When the cats get up to operating temp is when they work the best. Hence why cold starts are loud since the car is trying to heat up the cats more rapidly.

Right, this is why CATLESS cars smell like fuel when running but eliminating the fuel smell is exactly the purpose of a catalytic convertor.

In regards to cold starts, the reason they are louder is because the car hasn't had a chance to take any temp/o2 readings so it assumes that everything is cold and doesa few things. It opens the wastegate if the car is equipped with one, it retards your timing and it runs a richer air/fuel ratio. Because of this richer mix the engine is also programmed to run at a higher RPM to help burn off any excess gas that may be in the system because of this rich condition. After about 20 seconds the car has had enough time to get air/fuel temps and readings and stabilizes you're idle and air/fuel trims.

Smelling gas on startup is NEVER normal with a proper exhaust system so OP if you aren't catless you have a problem on your hands.

[davidr3]

Originally Posted by njdangelo

Right, this is why CATLESS cars smell like fuel when running but eliminating the fuel smell is exactly the purpose of a catalytic convertor.

In regards to cold starts, the reason they are louder is because the car hasn't had a chance to take any temp/o2 readings so it assumes that everything is cold and doesa few things. It opens the wastegate if the car is equipped with one, it retards your timing and it runs a richer air/fuel ratio. Because of this richer mix the engine is also programmed to run at a higher RPM to help burn off any excess gas that may be in the system because of this rich condition. After about 20 seconds the car has had enough time to get air/fuel temps and readings and stabilizes you're idle and air/fuel trims.

Smelling gas on startup is NEVER normal with a proper exhaust system so OP if you aren't catless you have a problem on your hands.

Yeah true, he very well may have some type of exhaust leak. I'm just saying in some others cars you encounter a fuel just for a quick second or two on cold starts but goes away quickly after.

OP I suggest searching for codes to start.

[Astone22]

Thanks for the quick responses! It is only for a brief second on startup. I have no idea where to look for a leak?

[auburnf30x]

It's hard to say. If you feel inclined I would remove the beauty covers off the top of the engine and look/smell for anything obvious. If that doesn't turn up anything, leave the covers off and have someone else start the car while you keep an eye on the engine bay. Also, as mentioned earlier, scan and see if any error codes are stored. Not all of them will cause a check engine light.

[Livetodrive]

Not normal. I wouldn’t garage it until the leak is repaired.