1994 4.3L vin W surging. Service Bulletin recommend upgrade to BPLC.

[billygraves]

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[craigger]

billygraves, thanks for you reply.
Both of the 2 new O2 sensors cycle hi/lo. The O2 to exhaust is clean connection as had to tap the hole after the bad original one came out hard (3 pound hammer and pound pound pound).
I just used the anti seize compound that came on the sensor.
Both the spider injector that was in it when I got (the previous owner said he had replaced it) and the one bought at Knechts produce the same results and both seem to work. I replaced his because I couldn't find why it was running rich and didn't trust his repairs (instead of replacing the nut kit, he put in rubber fuel lines with hose clamps. so i replace spider assembly and nut kit). Never found good reason for the running rich and bought a prom burner and changed tables so trims look good and no longer running rich. Now just the surging.
No problem asking about the gas. This problem has been around for several tanks of gas (76 gas).
The first of the two new O2 sensors was a Bosch and the second a Borg Warner. 3 wire, after exhaust y, just before cat.
WOT truck runs to high rpm. As never driven this truck without it having issues, I can't be sure of lacking power, but seems ok at WOT.
Looked over my saved logs and don't have any at WOT. I was always capturing low/med throttle logs for my surge problem. I will see if I can get a log file of WOT tomorrow.
No fuel leak seen with plenum off. Fuel pressure leak down, tests good.
Both new O2 sensors cycle hi/lo.
I recently have started with a 'original' copy of my bin file and 'retuned' it. No change.

[billygraves]

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[craigger]

I took if for a run. At WOT the O2 is not cycling, ~969mv.
During 'normal' cycling it's low ~60 - 70mv. Lowest seen 31mv. So don't think have O2 ground issue.

I would love to try the New Prom, but where can I get the bin file? I can't find it.

I have previously block off the egr valve, no help. During tune runs I disable the EGR in pcm with coolant cal, no diff on surges.
The evap canister is vacuum controlled on mine, I have it disabled for troubleshooting. So no effect.

Carbon on the exhaust valve stem is something I have thought about because I has the history of running VERY rich for unknown periods.
What would this look like on a scope? My electronics bench scope died in the time sweeps I need, so I bought the cheap Hantek 1008C.
Slow and not enough memory, but I can get waveforms.

I haven't pulled valve covers and so haven't checked valve tension. Put on my to check list.
Thanks for the thought on the rear block grounds. On mine, they are grounds for the pcm. I have ran external ground wire to test, no help
Re the back half of the proms, I'm not sure what you mean. Compare of the code? The limp mode code/hardware?