Steve, you have the patience of a saint. I already pointed this question to the cap'n, so you don't have to explain the same thing over and over again.

Today, I made a strange observation again. You might remember my problem from the thread AFM pot. I made a little mistake there when I sad that EHA receiceves a current of 0 to -8mA which is 8mA when the engine sounds loaded. This should have been -8mA.

Anyways, last time I measured KonEoff a stable 10mA for the first 10s then switching to a stable 20mA (19mA). This happened again today. However, as always I forgot to memorize the polarization before starting the engine and hence turned off the engine again. When I immediately turned on the ignition, I saw the 10mA for 10s again. However, then the current didn't move forward to 20mA but to -7.5mA. I started the engine, turned it off, turned on the ignition: again a stable -7.5mA after approx 10s. What has happened? And is it common that I have these 10mA first?

My other readings were:
Computer side of O2 connection grounded: 10.5mA EHA
Computer side of O2 connection Cap'ned: -15mA EHA

Computer side of O2 connection grounded: 0.95V O2 sensor
Computer side of O2 connection Cap'ned: 0.02V O2 sensor

To my understanding this proposes a working O2 sensor, a capability to control and a mixture that is not too far off to be controlled. Though I am wondering about the asymetric EHA control capability (-15 to 10mA).

My primary problem was the EHA current fluctuating between 0 and -8mA. I assume that the -7.5mA problem started today, as it never happened during my 2 measurements before. As the parts I tested today seem to work, I would assume the problem to be either fuel pressure (differential pressure in AFM, system pressure), a wrong mixture that is hard to control or something I don't know. Would you agree that if the sparks, the injection valves or the idle valve would be the problem, the rough idle would occur also with EHA off?

Unfortunately I don't have the equipment to measure those pressures. Is there anything else I can do to narrow down the problem?

I really appreciate all the time you spend to answer our questions. For me it is also very interesting to follow your logic to search the origin of such a problem. I do have an engineering background, but as you know, the gap between theory and practice is in practice far larger than in theory. And with this car (W107 SL) I am very interested to learn what is happening behind the curtain.

Thanx a lot
Tom