'91 e34 M50B20 engine without o2 sensor!?

[molesz]

Anybody heard about any e34 bimmers with catalytic converter but no O2 sensor. Exactly is it possible that a '91 e34 520i with m50b20 engine has the converter with no O2 sensor at all?

[MarkD]

It's highly unlikely that a car with a catalytic convertor installed at the factory would not also have an O2 sensor. (but I suppose there is a chance that it is possible).
The O2 sensor is used as feedback to keep the mixture in the range required by the cat. When not in this range, the convertor life is usually much shorter.
My guess is that someone removed the O2 sensor from your car. That motor was never sold in a USA car, and only in the 1993 - 95 E36 in Canada so I assume you are somewhere else.

Mark

[Bill R.]

Anybody heard about any e34 bimmers with catalytic converter but no O2 sensor. Exactly is it possible that a '91 e34 520i with m50b20 engine has the converter with no O2 sensor at all?

[molesz]

I am actually in Yugoslavia but the car was imported from Italy and it was really made for the italian market. I have searched for the O2 sensor and there is nothing on the converter what could even indicate that somebody has been removing it. Not even a place to refit one. Ok. I have heard about "unregulated catalytic converters" (ungeregelte katalysator) which can reduce only about 65% of the engine exhaust pollution but also I have found out that the Motor Management System of my car has a circuit for the O2 sensor (dunno where to connect it if I buy a new cat.). Fuel consuption is by the book (and of course unleaded)... should I waste my time and money on refitting a new cat with O2 sensor?