M103 EHA and CO Adjustment Issues (KE Jetronic Experts Please)

[300EVIL]

Over the winter I noticed I was having some problems with my 300E. If I didn't activate WOT when floored, I would loose a noticeable amount of power. When I backed off to half pedal I was accelerating more than full throttle was (minus activating WOT).

I pondered on this problem and ruled out a bunch of components that may have caused this. From here I narrowed it down to the CO adjustment or the EHA.

I decided to tackle the CO adjustment first because it was easiest to get to. Knowing I set it 2 years ago to be at approx. 55% duty cycle , I checked it and seen a reading of only 18%! I then adjusted it to read 50% and it ran fine for the rest of the day. In fact, it ran fine for many days, then the climate changed. I adjusted it again and it ran fine. Then it got colder again and I had to adjust it a third time!

From here I summarized it had to be the EHA. I stole the EHA from my parts 124 and installed it in my 300E. However, before I installed the EHA, I cranked up the set screw on the EHA a quarter turn to the right get a rich mixture instead of stoch.

From here I noticed a remarkable difference. The engine had way less hesitation at idle and carried the power through all RPM's!!! I don't think the car has ever run this good since I bought it! It's truly amazing! Almost as fun to drive as the 500E.

On the other hand. I still have a small problem.

After a couple days of having fun with my extra HP I noticed the smell of the rich exhaust. From here I checked my O2 and it was reading 80% duty cycle in closed loop. I then proceeded in adjusting the CO back to 50% and the engine started stumbling....... So, I adjusted it back to 80% where the power feels good.

There is obviously something I'm missing here. I didn't think a quarter turn would create such a rich mixture at idle. Is this the case or is the rich mixture caused by something else? I like the new found power and don't want to loose it. Any ideas?
Thanks!
Adam

[mbdoc]

The EHA adjustment is VERY critical on an oxygen sensor car!

IF the differential pressure is more than the original 0.4bar that is pre-set by BOSCH then the O2 sensor will have to control the mixture more that it was designed to do.

Since you adjusted the EHA a 1/4 turn I would imagine that is happening on your car..

I always suggest that adjustment to be no more that 1/6 turn unless you have fuel gauges to see that differential fuel pressure.