So, rich at idle and lean at 2000 rpm... (archive)

Thanks again. Bought a new multimeter (not a Fluke) and found the O2 sensor provides 0.8 volts at idle but falls to 0.050 volts (thats right, not 0.50 volts) after running at about 2000 RPM for 30 seconds or so. Also the reading does not fluctuate the way you and others describe. I am going to bring the car tommorow for a professional injector "purge" and we will see if anything changes for the better. The O2 sensor heater is not working and I traced the problem back to pin #31 on the MCU that does not provide a ground to the relay. The coolant temperature sensor seems to be providing the correct Ohm reading, so I am stumped as to why pin #31 does not work, maybe that part of the motronic box has failed.
Thanks again.

Check for a cracked boot or leaky connections/fittings between AFM and intake manifold. With a leak between the AFM and the manifold, as rpm and manifold vacuum rise, that leak will worsen, and the AFM will read low, "tricking" the Motronic. If the CO set screw and/or AFM are off-spec, it's conceivable you could still have a rich idle condition.

So, maybe look closely for leaks?

As for the O2 sensor, sounds like it's working, even without the heater.

Good luck with the injector cleaning, and let us know how things turn out.

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