OK, if we look at what is happenning here. When you have the sensor connected, the car runs badly (too rich or too lean, would be nice to know) and the ECU "sees" 2250 ohms. When you disconnect the sensor, the car runs better (leaner or richer?) and the ECU sees infinite ohms.
I think that the ECU sends a signal through the wire and uses that to set the pulse width to the injectors (along with other factors). A longer pulse width equals more fuel, richer mixture.
One would assume that with low ohms the mixture is "normal" and with 2250 ohms it is "richer" (to promote better cold running) then infinite would give "very rich" mixture.
So could you have a lean mixture most of the time? What readings do you get from the O2 sensor? Might there be an air leak?
If you have the resources, it would be useful to be able to read the exhaust gas when cold and connect and disconnect the sensor.
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