Recorded the readings

Includes:
Sensor voltage output 0V
ECT average 90°C
Speed average 65mph
Loop remained Open Fault at all times

It's because ecu is programmed to totally ignore data from o2 sensors on hard accelerating(full throttle) and to use default values.The reason is that car always have it's maximum power when it needed and there is no risk that ecu will cut off fuel because o2 sensor reads too rich at the moment. Bt...

Your high positive trim shows engine running lean and ECU adding fuel to compensate. Then there's the sensor question. I'd look at the sensor with the scanner, if it's stuck on low then it's bad. To check that just release some propane in the intake, carb cleaner, etc. If sensor signal goes high th...

misha wrote:Did you crimped and seal them?I doubt that it had splicing box with it.Splicing box comes with universal ones and not always.

At first yes. Then I suspected there could be a connection problem, so I spliced the wires and made direct connection.

The only problem with universal o2 sensors is connector.You can't just solder the wires to old connector.They need to be properly crimped and sealed.Sometimes,universal o2 sensors comes with splice box. There was a few complaints about bad oem Bosch o2 sensors right from the box,so there is possibi...

Yes, it is a Bosch universal sensor. Bosch P/N: 0 258 003 222 As according to Bosch Catalog According to my o2 sensor catalogue,this numbers are matching with oem o2 sensor.Why did you wrote that it's universal? It fits to 850 2.0 b5204s '91-'96 2.5 b5254s Because the connector is different. My old...

misha wrote:

moacyr wrote:Yes, it is a Bosch universal sensor.

That's a problem.

Bosch P/N: 0 258 003 222
As according to Bosch Catalog

I'd use a scanner that can read live data, that will give you fuel trims, engine temperature and o2 operation. Also measure resistance of ECT when cold and hot. So I did. Short term fuel trim locked on 0%. Long term fuel trim locked on 25%. Temperature is OK (90°). Idle MAF 5g/s (is that normal?). ...

Misfiring is caused by a mixture issue, and o2 sensor merely responds to what it sees. I'd look at trims and go from there. Now if system doesnot stay in closed loop you may have a defective sensor. However, since car's hard to start I'd check ECT first. how can I look at trims? I dont know how to ...

Yes, it is a Bosch universal sensor.