When idling the truck will go rich for a couple of seconds.

[Jquest]

I have a summit truck cam in my 2008 ly5. Run 93 octane. I tuned it a while back and it's been running fine. I have everything turned on , so I'm not running
just the maf or VE table by itself. The computer should be keeping it at 1.0 ,which it does 99% of the time. Really happy with the way it pulls my boat.
Here is the thing. I have this one issue that I believe it's gotten worse.
When I come to a stop...the truck is idling and then it riches up for a couple of seconds. What I mean by that ...it goes from 1.0 to .86 or around there.
The engine stumbles a bit and then the truck/computer recovers and it goes back to stoich. It doesn't do it all the time, but it's starting to worry me.
Another thing it does is when I put gas.....it some times revs up a couple of times like it's relearning the fuel trims and then straightens out.
It will only do it once after putting gas and won't duplicate it again til the next fill up. It won't do it when I regularly start it up. I don't run my truck low.
Always try to put gas when it's just past half. one more thing I noticed...it appears that the truck idles better with the AC off, which is how I programmed the tables.
Any thoughts or suggestions will be appreciated that maybe I need to tweak something.
TIA!!!

[2xLS1]

Evap purging? Just a guess.

[leciphern]

that's a valid guess.

on some platforms (vw) the evap purge valve gets stuck open without triggering a code.

this creates a vacuum leak, however the engine sucks air from the end of the evap hose (at the rear of the vehicle).

clamping the evap hose shut on that platform would improve the idle if the purge valve had actually failed.

[Jquest]

Funny you guys should mention that. I did get a evap code a couple of months back. I replaced the canister. Could it be that the canister is a little skidish and not working correctly? AFter i got the code I replaced it , cleared it and that was the end of that.


iEdit: Thanks for the out of the box thinking guys. I replaced my canister from Jhina with an AC delco from Mexico. Seems to be running better.