Duty cycle Mayhem.....
 

Still messing with the duty cycle on my 86 300E and am still puzzled by a few things. My original problem was intermitent high idle, hot and cold, steady with occasional changes to another steady speed, always between 1400 and 650rpm. I started with duty cycle faults. None. I went to check duty cycles and, at Hot Idle (and I hope, closed loop) I get intermitent fixed 90.9%, then occasionally, I'll get a value that I can adjust by changing the mixture screw. It is hard to get a relatively steady closed loop reading. Tried to get the duty cycle reading between 40-50% but the damn thing goes all over the place. After being able to corner it in the lower 40"s, it starts to drop slowly until it hits 7.5%! and it goes back to Idling high for a minute or two, then back to the 40-50% range. I am out of ideas, but here is what I know 1)the EHA current is all over the place idling, Key on, engine off, it reads 13mA, 20mA is about right I am told. Idle speed control is at 300mA idling, duty cycle from 45% to occasionally as high as 70% 600-700 mA is normal I am told. What the hell is going on here? I got the car with the Idle problem and can't seem to get a base line to work from. I have disconnected the Oxy Sensor and got the light after a 3 mile drive and the car ran like crap, is my sensor weak? Any ideas would be great! Thanks

PS I live at 6000 ft....... do I need to get a new Zero for the mixture (and disable the altitude sensors).