Slight idle bounce 2004 chevy 8.1L

[recycleoldgrowth]

Just recently replaced my alternator thinking because it's diodes were going bad was why my idle was rough. Turns out that was not the case. The voltage swing is gone (except now when the idle drops, so does the voltage) but the idle bounce is still there. (We're talking from 600, to 500 then back every couple seconds)

I've replaced plugs and wires, cleaned the MAF and TB, all grounds ohm out, there isn't an EGR valve on this truck to clean or replace.

I've looked at the live data using my scan tool. The STFT and LTFT on both banks are within +-5% and all O2 sensors read .2 - .85 with a good throttle snap. All closed loop data, idle is more or less perfect on cold start up OL.

Any other ideas? Appreciate your time and thoughtfulness on this matter.

Regards,
Kyle

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[79jasper]

Being electronic throttle body, I doubt it has a idle air control valve.
Could be a vacuum leak.

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[recycleoldgrowth]

It has an Idle Position Sensor build into the TB I believe. Not sure about a vacuum leak only because the STFT and LTFT are with +/-5%. I guess I could take a can of brake cleaner to it.

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[recycleoldgrowth]

I just had time to review 3 sets of live data across multiple RPM ranges I'm seeing a common thread.

The LTFT on both banks seems to me to be very lean at idle -9% to -14% (not getting enough air?) At higher RPM'S it reading +5% to +9% (getting to much fuel?) I was under the impression that LTFT should stay pretty much the same even with added throttle, am I wrong?

The STFT stays pretty much +/-6% on both banks.

Is this pointing to a bad throttle body assembly or a MAF on its way out (No codes).

Both O2S2 are not holding a consistent voltage through a range of RPM'S, it's ranging from .295 to .820. Shouldn't they also be hold a consistent voltage as well? Or is that just at idle? Both O2S1 seem to be doing their job right. Bad CAT'S or defective O2 sensors?

Thoughts?

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