Think about it for a sec. How does the ECU act different in closed vs open loop? In closed loop, the ECM looks at temp sens, mas air flow, MAPS, and throt position, but ignores O2. In Closed loop, it starts believing O2 sensors. If one is bad, that is the moment of rough running. O2 sensor is the problem. Here's how to prove it; Unplug both O2 sensors. If it runs smooth, you've found the prob.

 

That's what it looks like. I tested the ohms on the front one and got no reading. That would explain the lean reading on the rear one. The engine is trying to go lean because the front one says it's too rich. I'm starting to understand these computer systems.

Now, how do you remove the 6 rusted on bolts on the exhaust manifold without breaking them off? The threaded ring for the front sensor twisted right off ... with the sensor. Can't wait to do this one.

 

alright all finished. I ended up buying a stanless strap-on O2 bung (I guess that's what they call the threaded ring.) from Summit Racing near Akron, Ohio. Cool place. I also had to buy a new catalytic converter. The old one was rotted. Put everything back on and runs like it should. Must have been th O2 sensor. I never checked the EGR. Now its off to E-check.