I’d like to add some content to the above ‘i.a.’ :... Regarding running behavior, however, a slightly further opened EHA with its current fluctuating around a mean value slightly below ‘0’ mA at idle, which is represented by a duty cycle fluctuating around a mean value slightly below 50%, is better. That has i.a. to do with the in post #1 mentioned better leaning than enriching capability of the EHA. A duty cycle at idle fluctuating around a mean value of about 47% or a little lower is usually a good choice for an intact KE-Jetronic in my experience. ...
Another reason for a duty cycle preferably below 50% is contamination.
Deposits can, for instance, narrow the 0.2 mm (~ 0.008“) wide vertical metering slits through which the fuel flows from the control plunger side into the upper chambers of the fuel distributor’s pressure differential valves. With the control plunger set to a slightly higher position via Lambda adjustment screw, these metering slits are a little wider open, which, as described in detail in post 1, in order to continue to receive confirmation of the correct air/fuel mixture (λ ~ 1) from the o2 sensor, is compensated via EHA control by more negative EHA current (lower duty cycle). Depending on the degree of contamination an adjustment to a rather low duty cycle might be beneficial for the engine’s running behavior.
However, if the degree of contamination in the fuel distributor requires a duty cycle below 35% to achive the best possible running behavior, and if a fuel distributor replacement or refurbishment does not come into consideration, changing the mechanical adjustment of the EHA’s baffle plate might be an option.
But, like refurbishing the fuel distributor, it requires adequate knowledge and significant care, patience and cleanness ! … I would not recommend to touch that tiny EHA adjustment screw if the EHA is looked at as a “black box” attached to another “black (gray) box”. :wink_2: … I’m thinking about creating a separate detailed thread about checking and changing the “EHA adjustment”, similar to this “duty cyle adjustment” thread.
Talking about contamination …
The KE-Jetronic is not overly enthusiastic about ethanol containing fuel, especially when the car sits a lot. I recommend not to put the car into hibernation for a couple of months with the fuel system filled with fuel containing more than 5% ethanol ! … If it’s unavoidable, I recommend at least to use a good and proper fuel additive, which I recommend in case of fuel containing more than 5% ethanol anyway, even if the car is driven long distance every day.
Ethanol containing fuel can lead to increased deposit forming and to acidification, which can lead to corrosion of the aluminium … and aluminum … parts of the KE-Jetronic.
There are fuel additives on the market which promise to prevent these effects and which, aside from the corrosion, even promise to reverse them … and I don’t say they don’t.