I have an 06 cobalt ss/sc with stage 2. Once every few feeks my check engine light comes on and gives me a system lean code; it usually occurs under a half of a tank and then when I fill up a few key cycles make it go away.

Accompanying this is gas smell outside of the car that only appears after I shut off the car. There is no specific place it seems to be coming from and no visible fuel leaks. I am also getting the same fuel mileage ~30mpg (a lot of highway driving) so I think it's some sort of vapor leak.

Has anyone heard of this? I am practicing the if it aint broke don't fix it mantra because it still has full power and full fuel economy. I'm thinking it is something to do with the evap system, although I would have thought I would get a code for it specifically.

My guess is a possible leak in the fuel system somewhere and when my gas tank gets down to the point that the purge valve activates it is throwing the lean code similar to if you leave the fuel cap off. What do you guys think?

 

i had that happpen to mine.and my fuel pump was broke

 

At my work we have a 07 SC and it keeps throwing this code and last time we talked to the Chev dealer they said they're thinking its the fuel pump (not confirmed yet), so the above may be on the right track.

 

if it was evap you would get an evap code, unless you have codes deleted.

 

Very possibly a broken canister/line issue like what was happening on the later cars. It leaks, but only a very small amount, so you smell it but it doesn't do much else. Wouldn't really explain the codes though...

 

if u have an aftermarket air filter (airbox mod) or an aftermarket intake that will throw the system too lean bank 1 code. just makes the car think it's running too lean which it quite possibly could be being that the gm stage 2 is just a flashed tune. every car reacts differently so a flashed tune may work great on car A but not good at all on car B. I'd check ur injectors just to look for any leakage and if you don't see anything i'd look into getting a custom tune cause that will for sure get rid of the too lean code if it is due to an air filter and you'll make more power and safer power.

 

Get your fuel pump checked.

 

I have the same problem going on with mine. However, my fuel pump is fine. I am checking into the modular reservoir assembly (MRA). According to some GM tech in Arizona, there is a defect in which it may crack. I plan to look further into this and will let you know if this may be an issue.

 

Great, thanks for your help everyone. I have been so busy lately that I haven't had the time to check it out myself. If anyone hears anything let me know.....otherwise when I find something out I will update the thread.

 

That is what we are talking about when we say fuel pump. Obviously not the pump itself, as it is a small unit deep inside the tank, but the canister that holds it, the regulator and the other components in the tank. The plastic on the top can crack, causing a leak, and there is a bulletin out to this effect, GM will replace the affected pumps under warranty.

 

This was broken when I bought my car, went back to the dealer 2 days after I got it and they said I was lucky my car didn't blow up....hardly but still I had a puddle on top of my tank.

 

Ahh, I see. We had similar issues on Mercedes when I was a technician there.....those fuel pump modules were 500 dollars a piece. I hope ours aren't too expensive if that is indeed what it is.

I feel bad for neglecting the car but I have been so damn busy I haven't even been changing my own oil.

 

Just dropped my tank today. It actually turned out it was my fuel pump. Good to go now

 

I talked to Chevy and since I live in a "warm weather" state the repair is covered by Chevy. I am almost positive that this is the problem. After posting this thread and getting an idea I can obviously smell it the most strong near the rear fender wells.