Tighten Gas Cap/Stall

[strutaeng]

Probably more than one problem going on... I'd focus on the stalling and crank-no-fire, personally; that's more critical and can/will cause driveability issues. Fuel pressure gauge test.

The gas tank message is probably not related to that, and EVAP issues typically don't cause driveability issues.

 

[Fless]

I pulled over and left the tahoe running to check the gas cap and there was a good amount of pressure on the fuel system.

Was this "pressure" or "vacuum?" Was the tank exhaling or inhaling?

 

[Stage2Tahoe]

It was pressure. I still haven't resolved the problem completely. I haven't had anymore stalling or hard start issues... However, I did get my first p0455 code a couple of days ago.
I have replaced the gas cap and still got the code, but not the tighten gas Cap. So last night I reinstalled the original gas Cap, and replace the purge valve. Then on the way to work this morning I got the tighten Gas Cap again. I will have to drive a little longer to let the system cycle before I will know if the Purge valve fixed the p0455 code. I blew air through the old valve and the valve seemed closed in 1 direction and made a sound like a wet fart when I blew air through the other side. I am guessing I am going to need to replace both to resolve the problem.