OK, some updates..

I used another multimeter today and checked the EHA current again - since I have a '91 300CE with basically the same system, I was able to compare results.

Using an older Sears multimeter - model 82015 - I was able to get 20 mA's at the EHA in my 300CE with KOEO. For some reason, I guess I can't figure out my newer Sears that I bought with the duty cycle feature - model 82139. With it, I initially got 2.72 mA's - I think...?

Using the older multimeter with my 560SL, I get 75 mA's with KOEO (According to the FSM 07.3-121, 75 mA's is correct with KOEO) - once the engine starts to warm up it drops back down and hovers around 0. I have noticed a hissing noise, air escaping from around the air sensor plate. I decided to try and adjust the mixture - after some fiddling I got the duty cycle to hover around 50% and the EHA current to center around 0 mA's. The idle evened out and isn't nearly as "rhythmic" and the duty cycle does not go to 90%+ now - BUT, the idle speed has increased some, to about 900 rpm in park and 750-800 rpm in gear.

Am I getting closer?

__________________
RG Newell

1984 300D
1972 250
1986 560SL
1991 300CE