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M42 Rough Running

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    Interesting. My car is UK spec with no CAT or O2 sensor (C132 plugged in at bulkhead) so it never goes into closed-loop? Does the DME still put the car onto different maps depending upon the information from the blue sensor?

    Unfortunately blue sensors are on back order with BMW here so I'm going to put the intake back together and see if the problem is fixed, at least the blue sensor is accessible with everything back together if I have to revisit it later.


      Correct, your car runs in open loop at all times in that case.

      The blue coolant temp sensor definitely still plays a big role in warmup enrichments and whatnot. There are not separate "cold" maps or anything, but the engine temp does get used as a term for adding additional fuel to the base calculated quantity when cold. On cars woth O2 sensors, it also gets used to determine when to start closed loop operation.

      I am not sure what sort of multimeter you have, but do try to check the resistance. While failures are uncommon, you may as well get an idea of whether or not it is giving you more trouble.