Weird gas pumping issue

[Bsb120]

I bought my 2008 ltz about a month ago, I’m getting a pending dtc that eventually just turns into a dtc, p0455
(Large Evap system leak) gas cap is tight seal in it looks good. Now the weird part is I can’t just pump gas. Every couple dollars you hear a sputtering sound almost like air is going in then in a couple seconds It cuts the pump off. So it’s taking forever to pump. Is this a common issue? Is there a fix that’s not gonna kill my wallet? Could this be why I’m only getting around 12 mpg?

 

[HiHoeSilver]

I bought my 2008 ltz about a month ago, I’m getting a pending dtc that eventually just turns into a dtc, p0455
(Large Evap system leak) gas cap is tight seal in it looks good. Now the weird part is I can’t just pump gas. Every couple dollars you hear a sputtering sound almost like air is going in then in a couple seconds It cuts the pump off. So it’s taking forever to pump. Is this a common issue? Is there a fix that’s not gonna kill my wallet? Could this be why I’m only getting around 12 mpg?

Yes, it's common. Assuming your gas cap is good, it is likely either:
1. A bad charcoal canister, which may also have sent charcoal pellets into the evap lines and clogged them.
2. A bad vent valve.
3. A bad purge solenoid.

 

[Doubeleive]

usually guys just save themselves the time, pain and misery and just replace all 3 parts (shotgun it) and 99.9% of the time that fixes the problem
by the time you pay for the diagnostic and labor to replace the one bad part you could replace all 3 for the same price and not have to worry about it again for another 10yrs

 

[Idriveaho]

Mine surprisingly got better. The last few fill ups I haven’t had to worry about it shutting off.

 

[Bsb120]

I see the Evap purge vss as live is not really expensive nor hard to change but what about the other 2?

 

[OR VietVet]

I wish I could tell you how difficult it is but I have yet to have to do them. I got tired of not knowing and signed up at ALLDATAdiy.com and it walks you thru repair times and steps and diagnostic info for your rig. Also, there is you tube to get an idea of the steps and difficulty. What Wes said makes sense on all fronts. The parts are not that bad and if you do the labor it is good for a very long time. Replacing one part of three that work together can cause problems down the road when the weak link steps up and starts this process all over again.

 

[Doubeleive]

I see the Evap purge vss as live is not really expensive nor hard to change but what about the other 2?

ah it's not that bad, drop the spare, the tubes to the canister and valve are quick disconnect, take off the old ones, put on the new ones, it helps if you disconnect the filler tube from the body and pull it down from the inside to hook up the new filter & tube, then shove the filler tube back up and re-attach it. the one under the hood on the intake only takes a couple minutes super easy. if you are reasonably talented it shouldn't take more than 30-45 minutes from start to finish.
helps if you watch a couple youtube vidoe's so you know what to expect.

 

[HiHoeSilver]

ah it's not that bad, drop the spare, the tubes to the canister and valve are quick disconnect, take off the old ones, put on the new ones, it helps if you disconnect the filler tube from the body and pull it down from the inside to hook up the new filter & tube, then shove the filler tube back up and re-attach it. the one under the hood on the intake only takes a couple minutes super easy. if you are reasonably talented it shouldn't take more than 30-45 minutes from start to finish.
helps if you watch a couple youtube vidoe's so you know what to expect.

Lol @ "reasonably talented"

 

[Doubeleive]

Lol @ "reasonably talented"

ya, some people seem to struggle with it

 

[drakon543]

also does the gas cap look like an original gm gas cap or an aftermarket one? not directly suggesting its your problem but if your going to shotgun it and its not original. only a month of ownership just makes me wonder if it may have popped up once or twice for the previous owner. if they put an aftermarket gas cap on there it might be adding to the real problem. the aftermarket ones tend to be 50 50.