Maybe only Bosch or VW engineers know this, but = the list has amazed before...Over the past few months, I have run our '88 with = the O2 sensor disconnected (open loop). I did this so that I could = manually adjust the AFM spring tension and wiper static setting and live with it = awhile under various conditions without fighting with the ECU. Lots of = fiddling later I do have open loop settings that allow the WBX to run = right. Rock steady idle (though cold is still an issue) and plenty of power. = Today I again connected a digital multi-meter to the O2 sensor while still = keeping it disconnected from the ECU. This setup allowed me to drive = with the multi-meter propped on the dash. I had found earlier = that our engine will not run right (too lean, stumbling acceleration, lousy = throttle response) with O2 sensor outputs in the .5 range where I had seen the = list suggest that they out to be. I find that my manual S.O.P. (seat of = the pants) adjustments have left me with O2 outputs in a fairly = constant (doesn't fluctuate too much) .75 to .88 range. I next reconnected = the O2 output to the ECU while keeping the multi-meter connection piggy-backed = as well. Now the O2 output changes quickly as = the ECU is trying to adjust. Output appears to go from .55 to .90. A = little more lean hesitation at lower rpms, but the high rpms seem to run more cleanly.

My question (finally) is: what O2 sensor = output range is considered normal with the ECU adjusting things? I thought = that the O2 sensor / ECU combination attempts to adjust for no excess oxygen or a = 0.00 voltage. Our WBX might run at this level, but it would run = terribly. At what output levels does the ECU go "out of range" and give up = defaulting to open loop again? With non-spec AFM settings am I forcing it = to go open loop or even fluctuate between open and closed?