At 01:40 PM 9/26/2008, Jim Felder wrote...
>David, as I just wrote to Larry A., it climbs to around .843 and stays
>there as it runs rougher and rougher.

If the closed loop adjustment is working, the voltage should move back
and forth across ~0.45V. They are extremely sensitive, a tiny bit lean
and it will be well below 0.45V, a tiny bit rich and it will be quite a
bit higher. If it sits at one reading without moving much, then the
fuel control probably isn't working right.

If your's is steady at ~0.8 volts, AND the engine is running rich, it's
not the sensor, it's something else. If the sensor were bad and putting
out that voltage, the ECU would be make the fuel mixture leaner (and
it's probably trying to do so now).

Have you checked the fuel pressure? If the regulator is bad and the
pressure too high, that might cause an uncorrectable rich condition.

You might also try unplugging the cold start valve (aka "fifth
injector"). If that's always on for some reason, it would make the
engine run rich. It could also be leaking, in which case unplugging it
wouldn't change anything.