Pre-Cat Oxygen Sensor, Bosch - E32 750iL, E31 850i (11781733628)
Bosch Oxygen Sensor - 11781733628
E32 750iL, E31 850i pre-cat O2 sensor (located before the catalytic converter).
The pre-cat O2 sensor, also known as a Lambda probe, on the 750/850 is one of the most important sensors on the M70 engine. The pre-cat sensor tells the engine computer how well the engine is working (note: not how clean the emissions are). The pre-cat sensor gives the ECU feedback on the engine tuning - if it's running lean or rich - and the ECU makes adjustments based on its data. The ECU adjusts fuel injection based on the data so the sensor also affects fuel economy in addition to performance. An integrated heater circuit helps prolong the life of the sensor but can also fail and give a check engine light.
Signs of an O2 sensor failure include worse fuel economy, lack of torque, hard starting, and fault codes for the sensor(s). It is a good idea to replace the O2 sensor at regular intervals rather than waiting for a failure. Since the performance degrades over time you may not even notice the loss in performance or economy.
This is a genuine Bosch 750iL 850i 850Ci O2 sensor. Bosch is the original supplier to BMW for oxygen sensors, as well as the original inventor of the O2 sensor. Both 750 and 850 take two sensors.
E32 (88-94) > 750iL
E31 (91-97) > 850Ci