Hello Harley:

The 02 sensor signal isn't used until the engine warms up, so it isn't likely to be the culprit when it is cold. In any case, though, you should measure its output when warm to see if it is good. Run the car till warm, pull back the black boot covering the spade connection in the engine bay (the one with the single green wire, not the two white wires which go to the heater). Using a digital volt meter, put the positive lead on the connection (leave it plugged in) and the negative to a good ground. If the 02 sensor is good, it should produce voltages that vary between about 0.1-0.8V at a rate of about once per second. Constant high or constant low are bad (one indicates rich all the time the other indicates lean all the time). There are good details on further checks in the 700/900FAQ in the FEATURES pull-down menu...

Have you ruled out intake manifold/injector seal leaks?

Good luck!

Herb Goltz, London, Ontario, Canada '89 760GLE w/171K mi