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?