Tinker,

I consulted my local MB mechanic who does work evenings out of his garage at home. He deduced I had turned the adjusting screw so far it was no longer useful to try to read the lambda numbers. Apparently once you get far enough out of whack the adjustment screw produces random or at least inconsistent results, which leads to more mis-adjusting. His cure is to unplug the EHA connection and tune it by ear to a high, smooth idle. Then plug the EHA back in and start tuning with the lambda adjuster, in small increments. Well, I didn't get the car retested, but my younger son (the one who's car was the subject of this thread) made the adjustments and the engine runs at a 0.5 +/- .05 or so and smooth as silk. No excessive stink from the tailpipe.

The next step, assuming the car fails emissions testing tomorrow, is to check the injector spray pattern. According to the mechanic, no lambda adjustment can counter an injector or two that is not properly atomizing the fuel as it is injected into the intake manifold. I will post the results tomorrow. Jim

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Own:
1986 Euro 190E 2.3-16 (291,000 miles),
1998 E300D TurboDiesel, 231,000 miles -purchased with 45,000,
1988 300E 5-speed 252,000 miles,
1983 240D 4-speed, purchased w/136,000, now with 222,000 miles.
2009 ML320CDI Bluetec, 89,000 miles

Owned:
1971 220D (250,000 miles plus, sold to father-in-law),
1975 240D (245,000 miles - died of body rot),
1991 350SD (176,560 miles, weakest Benz I have owned),
1999 C230 Sport (45,400 miles),
1982 240D (321,000 miles, put to sleep)