NEED HELP Stalling coming to a stop

[Redbeard]

"But heck, I hate all "acronyms"."

I totally agree with this! I do wish folks would Spell It Out the first time in every document they write and not ASSUME we can read their mind to what the acronyms mean.
This site helps me with acronyms:

Abbreviations and acronyms dictionary

Acronym Finder is the largest and most trusted database of over 4 million acronyms and abbreviations. What does an abbreviation stands for? The answer is here

www.acronymfinder.com

 

[Street]

Good Day,

Two comments:
first: the O2 graphs look spot on for the upstream, upstream should rhythmically cycle between near 0 and 1V, very close to a sine wave. Downstream should be fairly steady at .6-.8V if the Cat is working as intended.

second: Your 4.2, like mine, has very low manifold vacuum. My local GM tech has told me that it should be at least 10psi, 13psi is ideal; mine is 5-6psi and I think I saw 8 and less on the data images posted. My VVT is also not coming back to 0deg at idle causing stalling and a nasty stumble coming off idle. Both symptoms, he said, are related to the cam not fully returning to 0deg.

Something worth checking out in diagnosing the stalling issue.

 

[TJBaker57]

my guess based on the SM..... SUC... system unit cooling (ie. coolant), SUM ... system unit metered (ie. incoming air). But heck, I hate all "acronyms".

I think you have it. I had "Start Up" in mind from some vague memory of reading something somewhere which led me to Start Up Coolant but got stuck on the "SUM".

Yesterday I loaded up some documents I had deleted from my phone to free up memory and dug through them to find this for a later model year. This is for the P0442 but is quite similar to the P0440.