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'07 Subaru Outback 3.0R 5 speed auto. I am logging using the excellent RomRaider and was kind of surprised that when graphed RPM looks like a square wave in most situations, don't know if it was doing this before. The first chart covers 8 seconds at 50 readings per second, the second lower RPM's at 20 readings per seocnd. Is this normal ?

50kph, second gearenter image description here

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  • I don't believe the plot is "real". I would guess something in the electronics or the sensor has failed giving the nonsense data, and the rough running is the ECU thinking the nonsense is real and trying to modulate the fuel flow rate to stop the apparent oscillations, or something similar.
    – alephzero
    Sep 12, 2018 at 20:22
  • Can you verify this with another scantool/software?
    – Ben
    Sep 13, 2018 at 0:34
  • Definitely could be a logging/sampling issue. The car has a drive-line issue so will update here after fixing the car and logging over again.
    – ajayel
    Sep 14, 2018 at 20:19
  • maybe due to the way the crankshaft position sensor works reading teeth on the crankshaft plate ?
    – ajayel
    Jun 21, 2019 at 6:43

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