Rpm bounces while moving

[Husky05]

The rpm drops 2 or 3 times within 2 seconds.

I can adjust the log rate to 20 milliseconds, I usually run 1 seconds. I can try 20 milliseconds.

However I noticed idle rocks my truck 2 or 3 times then steady and do it again. I've attached shot of the data. That's idle no touching anything. That's how much the voltage bounces from minimum to maximum numbers. I guess it's supposed to be steady at idle?