Yukon/Tahoe Performance

[honkon]

Swap front oxygen sensors from driver to passenger side and passenger side to driver side. See if the issue follows the sensor. If so, replace sensor. If not look for wiring issues and such.

Sent from my HiDiNg PlAcE

I tested the o2 circuits and I'm reasonably confident that I'm looking at a bad o2 sensor. Not gonna swap them around when new GM sensors are $28 a piece and getting them out is most of the trouble. The sensors on there look very old so they should be replaced anyway.
Attempted to replace them today. Bank 1 came out without any drama, new sensor installed and connected. But the Bank 2 sensor ****** up the bung out on its way out. Tried to straighten out the threads by installing the new o2. No luck. Now I have a bung and a new sensor both with ****** up threads. Pain in the ass.

 

[Supercharged111]

I bought a tap and thread chaser for that very reason.

 

[honkon]

I bought a tap and thread chaser for that very reason.

I have a tap set. Not sure if there's clearance to get at it with the y pipe on. Might have to take it off.
That would make it my 3rd set of exhaust manifold flange donuts in about a month. I've been having trouble getting them seated up good since putting the transmission in. Are those considered reusable? I think they're fine to reuse unless they fall out of the manifold. Then you can't get them put back the same way they were. Unless you get lucky.
I'm planning on buying a knockoff Tech2 as well.

 

[honkon]

Had to remove the y pipe and install a new o2 bung. PITA but its all put back together now. And I'm ashamed to say I made the wrong call on the o2 sensor.
Bank 2 o2 activity is pretty much the same as it was with the old sensor. Looking at it closer, there's some strange problem that will make both bank 2 sensors stick lean, at near 0 mV. Then they'll pop back to life and stick around 420mV, reacting very little to any change in conditions. Fuel trim doesn't reflect this activity at all.
And all of this is happening with no discernible affect on drivability while bank 2 is purportedly in closed loop fueling. This baffles me. I'm questioning my scan data.

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This is what factory exhaust minus cats sounds like. Sounds like it's missing a little don't it?