Hi Dave,

Yes you got the major thing fixed. The gross mixture control is working -- now the fine control provided by the oxygen sensor feedback needs fixing.

I agree the oxygen sensor seems to be working, and your pink wire should follow it lean if you fake it out with a ground (low voltage) but the mixture remains rich and out of the range the ECU can adjust it leaner.

My first concern and the easiest thing to test is the oxygen sensor. The single wire sensor is cheap and requires regular replacement. Can you dial in the mixture with a fresh, un-sooted oxygen sensor? If not, there are other causes of rich mixture outside of the range closed loop can adjust for, such as fuel pressure, leaky injectors, exhaust manifold gaskets.

It might explain the lack of idle bypass control. For that, try blocking the idle control path. With it blocked you should be able to dial that black knob clockwise until the engine stalls. If not, the throttle body might be leaking a lot of air past it.

The pink wire voltage is "digital" and isn't strong enough to drive an LED directly, like it does in the LH2.2 design. It is just another way to see the oxygen sensor's response, because back in the day mechanics didn't have high-impedance digital multimeters. So the voltage represents either lean or rich with no in-betweens. When it is in closed loop, the voltage will swing back and forth as the ECU corrects lean and rich to stoich. Today, it is just as easy to watch this happen at the oxygen sensor, but remember, it needs to be warm. Try raising the idle speed while watching, to see if it ever gets to the lean side.

What video?

--
Art Benstein near Baltimore

'Some people ask the secret of our long marriage. We take time to go to a restaurant two times a week. A little candlelight, dinner, soft music and dancing. She goes Tuesdays, I go Fridays.'