last update for anyone having this same issue. It ended up being both upstream O2s. Been driving it a lot hauling stuff and whatnot, and yeah it hasn't been acting up after I replaced the O2s.
Word of advice, even if you don't have O2 codes, check what your upstream sensors are doing. Mine would start at about 1v, and slowly drop to 0.14v and stay there, causing the truck to have no acceleration and jerk at idle like a big cam.
Oh, and last update, because I can't replace my bank 2 O2 without destroying the exhaust, I'm just gonna fab up a whole new exhaust for it. Long tube headers, 3" pipe back to the muffler, true duals. Should net me some nice top end, but more importantly let me actually have functional O2s.
Dud1f3r,
First of all, Welcome to the GMT400 forum. Although these trucks are older and can
accumulate 'tough to troubleshoot' issues if they suffered from benign neglect by the
PO, once you get them sorted out they can be a hard working faithful traveling companion,
and a hoot to drive to boot.
Second, a sincere thank you for returning to share what the final fix was. So many people
pop in, ask for troubleshooting assistance, and then never return to share what the machine
decided was the actual solution to the problem. That's too bad, because every person who
shares the results provides valuable feedback/insight to all of us trying to do our best with
the remote troubleshoot art.
And, yet again the solution supports
@Schurkey's recommendation to gain access to the
real-time data for these tough 'resisting repair' scenarios.
Again, thanks for closing the loop and sharing the fix. Hope we get to cross paths down
the road.
Cheers --