I heard a loud boom like something fell off into my exhaust. I smell gas at idle n driving. I don't see anything broken or any leaks. Any ideas please

 

What car do you have? If LNF, it's the evap purge. But that doesn't explain the gas smell.

 

Loud booms are bad.

 

Check the car, something in the fuel system is leaking. Does it start up normally after sitting for a couple hours?

 

Lnf 2005 cobaltss /sc
Starts up fine . no rough idle. No signs of leaks. I just smell fresh gas n my exhaust don't seem as loud as usual. Also no codes or lights are on and my gas guage drops faster than usual

 

Also after a few hours has a hard start up

 

The supercharged is LSJ btw. Have you checked your actual gas mileage (not what the display tells you, but miles/gallons when you fill up)?

It's doubtful that something is leaking INTO your exhaust without seeing a huge performance difference. The only place for that to happen would be at the injectors (stuck open, no spark, etc). It could be a leak near the gas tank which you are mistaking for the exhaust. Do you see any performance differences? Engine running differently?

 

From another thread

"a lot of 2006-2007 cars had issues with the fuel pump canister. the lines leading to the fuel filter crack and seep fuel"

There is a recall if you smell fuel. It may still be covered by the dealer as it's a huge hazard.

https://www.cobaltss.net/forums/prob...l-leak-253235/

As for hard starts I'm sure there is almost no fuel pressure as the lines have leaked most fuel out.

 

Ok update. After a week of smelling gas it just randomly stopped. Took it to a shop they found nothing wrong and it no longer smells like gas.
Now a new issue just installed racing 4-1 headers n all new exhaust gaskets. Now when I slow down it pops. I read that's normal and I have good air flow. Is this true? Also much appreciated for those who answered my post

 

If you are talking about popping out of the exhaust. Especially when decelerating, then yes that's normal when you start taking restrictions out of the exhaust.

 

I have the SRS exhaust with the silencer. If I remove the silencer n run really loud think it would stop. Could my silencer cause any air release restrictions

 

Took my 07 to the dealer he thought that was it and was gonna do it no charge.. turned out to be rusted hole in the fuel line($1100) be sure to check yourself before taking to dealer (if you can) I was getting about 280 miles per tank

 

Damn that sucks really bad.

280 miles per tank. Thats 22mpg. Wouldn't have really set me on to a leak except for the smell.

 

My bad that was when I was comparing to the 23 gallon tank in my old truck.. I wouldn't reset trip miles until I drove out 23 gallons such was 280. For the Balts 13gal tank it's like 180

 

Update. After about a week of worry. The gas smell went away. But I installed some Zzp headers and my old gasket was melted to crap. New gaskets and headers . problem solved. As for the loud boom. My mechanic thinks I had a huge backfire