The only data points I have for O2 sensors are:

1. From the CIS/E troubleshooting table, that says you should see a fluctuating .1 - .9V.

2. From a FI book that says a fluctuating .2 - .8V.

Two things may be happening. Your sensor is good, and your engine is running rich, except on a re-start and when it is going very lean. Or, your sensor is bad and sending a faulty signal. I would lean toward the former, but fi at 70K miles, the sensor has not been replaced, I would change it out with one of the generic Bosch units to eliminate the problem.

What is the on/off ratio doing - pin 3 on the diagnostic socket - at hot idle? Lots on posts on this.

__________________
Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe