Question on BMW 3-Series E36 O2_Sensor

Hello. Just had to replace a faulty injector on my 325i but the engine is still rough on idle before evening out. The mechanic mentioned that the oxygen sensor was probably contaminated - will this wear off or I will I need to clean or replace the sensor now ? Thanks

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[Nick at Pelican Parts]

O2 should not cause rough running on one cylinder. I would check for a misfire on that cylinder, spark, fuel, compression.

- Nick