My 2012 Mazda3 appears to have some engine difficulty in cold weather (below 10F) when at operating temperature. As I hold the gas pedal steady to maintain speed, the tachometer will jump back and forth by about 100 RPM. I can feel the oscillating change in speed as I drive. This occurs between 35 to 60 MPH regardless of the grade of the road, but is not noticeable when accelerating. I had the engine oil changed and cleaned out the air intakes in an attempt to get rid of some variables, but no change.

What could be the problem?

  • Not confident enough to make it an answer but it could be an issue with the distributor. Tachometers read the electric pulses from the distributor, so there might be something off there. Perhaps a good start is checking and cleaning the distributor cap and rotor? – MeltingDog Jan 17 '18 at 22:57
  • @MeltingDog A distributor? On a 2012 Mazda? These are COP. OP might want to check for TSBs, check the transmission fluid and do a TPS sweep. This sounds like rev hunting. – Ben Jan 17 '18 at 23:50
  • Haha - wasn't thinking. Was still in old car world. – MeltingDog Jan 18 '18 at 1:20

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