Tighten Gas Cap/Stall

[Stage2Tahoe]

Didn't really know where to post this. Move it if it needs to be somewhere more specific.

Here is the problem: I have be getting intermittent Tighten Gas Cap displays on the dash and I would pull over to re-tighten the gas cap. It would clear and I would go on with my drive. This morning however it popped up and when I found a safe place to pull over my tahoe died on me. I shut it off, Checked the Cap, and tried to restart and it acted like it was out of fuel. I cycled the ignition a couple of times and it finally restarted. It ran fine afterwards, but now has me questioning what is wrong now. Is this just a Gas Cap issue or do I need to start looking somewhere else. I know most of the newer vehicles are more sensitive to pressure changes in the fueling system, but I'm (as on my other posts) still figuring this thing out. Thanks for any help you can give.

 

[Fless]

Sounds like you have an evap code; have it read and post it here. Based on that, one of the evap components may be misbehaving, or perhaps the fuel pressure isn't up to par. You'll need more diagnostics to be able to zero in on the causes, and they may be unrelated.

If it gives you the hard start again, try using clear flood mode by holding the accelerator to the floor while attempting to start. If it starts right away, it's likely getting over-fueled.

Look at live data with a scanner and post up your long- and short-term fuel trims. Fuel pressure, too, while running.

 

[Marky Dissod]

Fire parts derringer, buy a new gas cap.
Don't run with under 1/4 of gas in the tank.
Don't top off when you fill up.
Be ready for more charcoal canister / fuel vapor recirculation issues.

 

[Stage2Tahoe]

Sounds like you have an evap code; have it read and post it here. Based on that, one of the evap components may be misbehaving, or perhaps the fuel pressure isn't up to par. You'll need more diagnostics to be able to zero in on the causes, and they may be unrelated.

If it gives you the hard start again, try using clear flood mode by holding the accelerator to the floor while attempting to start. If it starts right away, it's likely getting over-fueled.

Look at live data with a scanner and post up your long- and short-term fuel trims. Fuel pressure, too, while running.

It will be a couple of days before I can post a scan. I have to set up my PID's and graphs in my HPtuners if I share any info like that with you. You also mentioned an evap code. Does the 08 system show an SES light for the evap system? I ask because it never gave me any warning before it acted the way it did, and there was no light on the dash.

 

[Doubeleive]

It will be a couple of days before I can post a scan. I have to set up my PID's and graphs in my HPtuners if I share any info like that with you. You also mentioned an evap code. Does the 08 system show an SES light for the evap system? I ask because it never gave me any warning before it acted the way it did, and there was no light on the dash.

tighten gas cap is code for: small evep leak. It could very well be the cap but chances are more likely something else.
so, you could have both a evap issue and perhaps a fuel pump issue
I would advise monitoring the fuel pressure with a gauge or at least check it and see if it is even in spec for now
low fuel pressure would not normally throw a code but it would cause other noticeable issue's such as hard start, surging, stalling, etc

 

[Fless]

It will be a couple of days before I can post a scan. I have to set up my PID's and graphs in my HPtuners if I share any info like that with you. You also mentioned an evap code. Does the 08 system show an SES light for the evap system? I ask because it never gave me any warning before it acted the way it did, and there was no light on the dash.

Yes, between evap codes and misfires, they're the most prevalent issues to illuminate the CEL light.

 

[Doubeleive]

Yes, between evap codes and misfires, they're the most prevalent issues to illuminate the CEL light.

To elaborate a little more on the "tighten gas cap" message at this point the evap leak is very small, if the leak progresses beyond a certain parameter then it throws a evap code /CEL

 

[Stage2Tahoe]

Update: It has been 9 days since I started this post. I checked the gas cap and it seemed to be fine. I have filled the tahoe up a few times, and I've had no issues until this morning when the tighten gas cap displayed on the dash. 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. I am assuming then that the gas cap is indeed good. Is this a good indication that the evap canister may need replacement?

 

[lilairstrike]

Update: It has been 9 days since I started this post. I checked the gas cap and it seemed to be fine. I have filled the tahoe up a few times, and I've had no issues until this morning when the tighten gas cap displayed on the dash. 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. I am assuming then that the gas cap is indeed good. Is this a good indication that the evap canister may need replacement?

Try checking your Evap Purge Solenoid. I had this problem after filling up, it would sputter and sometimes take more than 3 key cycles to start up. I did have a CEL come up after a couple fill ups with the same issue. The solenoid located on the driver side of the engine compartment and can be taken off by hand. Check it by blowing into both ends of the solenoid. If it’s stuck open (air blows straight thru on both ends) then it needs to be replaced. I got mine for about $35 from O‘Reillys and you can change it in the parking lot.

 

[donjetman]

AC Delco purge valve

 

[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.