Not sure what to call this...

I've noticed that at a slow-speed idle crawl, my MCSA will start rhythmically surging/lurching at around 10MPH kinda like if you had a manual transmission at too low of a speed for the gear you're in before the engine starts to stumble.

It's not the engine, it doesn't stumble and RPM is steady, but it's strong enough to make my head bounce on the headrest. Doesn't feel like gear lash either.

I've noticed this on slight downward inclines in heavy traffic. I don't notice it going uphill when there's some engine load A bit of brake or a bit of gas stops it. Just occurred to me I should try popping it into neutral to see if that stops it as well..

Anyone else notice this? Maybe I'm just not used to having an automatic.

 

It sounds like idle speed control motor (that controls the amount of air going into the intake) is acting up which is common on high mileage cars that have not had any throttole body cleaning. So, it should not happen on newer cars.
Yes, shifting into neutral while coasting would isolate engine & tranny.

My MCS auto is not doing it...