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Went to swap one of the two up stream O2 sensors.In fact the one on the passenger side of Rufus.The crossover isn't in the best of shape and the bug for the sensor broke off.So now I'm driving without that sensor until I get a new crossover.Guessing the effect that has on the engine.Can't decide if it is going to run rich or lean.:confused:
Sensors upstream of the cat(s) are the feedforward signal, telling the ECM what's going into the cat(s), and the downstream is the feedback, telling the ECM what's going out the tailpipe. I suspect that with two upstream the ECM is going to have an averaging function, provided the two values are not out of limits, setting the rough mixture value on the average, and fine tuning on the feedback. With one gone the averaging function should default to a one-of-one selection, and you would not see any change other than a trouble code saying O2 X is out of range, or low. Of course this is a total guess, based on how other systems work. You might get a different answer from an S10 forum?
Thanks Roger. Appreciate it.