I'm also having a similar problem Like Pat. I have started testign all electrical components to see if they match up with what the manual states the values should be at. Now I don't know about the Voltage in the air flow meter potentiometer, but when i check the resistance on pin #1 and pin #2, I get a steady increase from 0.98Kohm to 4.83Kohms. This is a bit off from what the Service Manaul states, which should be from 3.8Kon to 5.6 Kohm. I see this as a possible problem since it would make sense that the computer does not see the Air coming in until the air flow meter reaches at least 3.8Kohm, and it hesitates up to that point, however since the entire scale is way off, the engine never performs how it should and hesitates and misses cause of a bad mixture. I already tested my EHA and it works like a charm. I have a multimeter hooked up next to me when I drive and I see the current through it at all times. The car hesiatates when the EHA current is at 0 and stops hesitating as soon as it starts increasing, well the higher the current the less it hesitates. I have read that the current should be a from 0 to 12ma, or so, 7-8 being the middle where the car idles. 0ma occurs when you let go off the gas, and my car does this perfectly but does not recover from this stage until it reaches around 2000rpm.
If anyone has any suggestions regarding this, or ran into a similar situation, or simply knows what should be happening and when, please get back to me, I'm still trying to figure this out.
oh yes, it's an 85 190E 2.3 8vlv