Engine races while idling

[krakoosh]

2017 with just under 110K. While stopped and idling sometimes the engine revs up for a minute or two then comes back down. Hot days with AC on... What is kicking on?

My '03 with 260K will do it sometimes as you accelerate and calm down once you get to 45 or 50 MPH. Again, hot days with AC blasting.

 

[LokiWolf]

Are you sure it is not the cooling fans? They are LOUD on the 15-17 when they ramp fully up. Hot days with AC running and vehicle sitting still are exactly when it would go full blast.

 

[krakoosh]

It's my daughter's truck and I've never laid eyes on it and am also ignorant about the 3.5. I'll have to get up to speed but appears to be normal for this year.

Very much appreciate the reply!