So my new Oxygen Sensor was not sending the correct signal ... it started at about .5 V where it should then as it warmed up over 15 sec. it just dropped like a rock to essentially 0 V (actually .03V or so) and just stayed there. This rather than fluctuating between .1V and .9V.

After Art Benstein's considerations I checked my wiring since it seemed it was somehow shorting to ground and everything checked out OK.

so befuddled I pulled the vacuum hose off of the FPR and saw no change until I put my thumb over the end of the vacuum line that just came off the FPR. Then the Oxygen sensor started to work normally - fluctuating as it should.

thumb off - sensor drops back to 0V.

this showed that the information the ECU was getting about mixture was taking it out of range of its adjustment ability (please correct me if I'm wrong here) therefore dropping the sensor to 0V?

in any case it was obvious the sensor was good and that I could get it to work by enrichening the mixture. Therefore I either had an intake air leak or incorrect fuel pressure causing the mixture to be too lean - Kevin and Brian's input greatly appreciated here.

According to Art there was an outside chance that the AMM was failing... so I took my spare 007 AMM and swapped it in and, lo and behold, the Oxygen sensor started to work just fine! I guess the old AMM must have been able to keep the car running good but not get the ECU proper information for the Oxygen sensor to do its thing.

now all I have to do is adjust the mixture pot on my "new to me" AMM,

all hail to the brickboard

thanks to Simon Kopacz BTW for the generous gift of an AMM he didn't need!

thanks to Art Benstein, Kevin O'Brien (6 Volvos...) and Brian Bridges (Fuel Pump) for their help figuring this one out!

Happy Jack,

why am I happy? because I don't have to buy (or try to make) a fuel pressure gauge adapter to check my fuel pressure AND I don't have to search around for intake air leaks! at least not yet!
--
jack, Bad Blue, '86 245, 245,000 mi.