recently bought a used 2017 CX5, it revved on it's own not to frequently in the beginning but once I went on a long trip and the revving was very frequent with burning smell. cold or hot start, even when starting after the car been driven for hours. Is this normal? Because the dealership took it back fixed other issues but says they have shown the car to 2 mazda garages and they said it is a characteristic of the car to do so. I am not quite happy with the feedback. Is this normal??

 

I've had similar problems, mainly when cold and without burning smell, runs up to 2000rpm when cold for about 40 seconds. The dealer says it's OK and typical of the CX-5. Bear in mind the red line on that engine is 5000 so I guess 2000's OK although I'd prefer it didn't do it at all. Great car other than that

 

The warm up cycling for a skyactiv engine it is aprox. 1350rpm during a cold start and the warm up cycle for the Ho2s is aprox. 45 seconds then idle down to 850 for about 10 seconds then normal idle speed when the Ho2 have reached open loop (no ECU input information) and also when coolant reaches 130F .
If after say aprox. 2 minutes if you are still idling above 800 rpm then you would have a active or pending DTC and can retrieve the DTC by accessing the diagnostic connector.