Unwanted acceleration at 1500rpm

2016 trd or dcsb auto. When I am in 1st gear and using the trains/engine to maintain speed if it drops below/at 1500rpms it will briefly accelerate till it hits about 2400 rpm and then start slowing down again. I have noticed that if I watch the eco screen that the bar goes from 30mpg down to about 15mpg until acceration stops. It happens consistently when driving downhill in my neighborhood and to a school nearby. Any ideas as to what this is? It has done this since purchase, I was hoping that it would go away. I did have the ATF topped off right after my 10k service. They didn't say how much they added but just top off.

 

Cruise control on?

 

Nope. Never use cruise control. Maui roads aren't long enough to need it

 

There is a thing called DFCO or deceleration fuel cut off. Above about 1500 rpm while you are slowing down your injectors are off and no fuel is used. Below about 1500 rpm it kicks the injectors back on briefly. You may be seeing this kick on.

Not positive but could be what you are feeling.

 

Auto or manual? Is it shifting when that happens?

 

Interesting. Never heard of this before. Will look into it.
Edit: I had no idea that this was something implemented so long ago. It does seem as though that is exactly what is happening. I just never noticed it in any other vehicle. So it would seem as though on my downhill with no throttle the fuel is being cut and then when it hits that 1500 rpm threshold then it kicks the injectors back up and it picks up till 2400 rpm and goes into fuel cut again. Kinda disappointing as I use engine braking daily coming down the hills. Gotta try and keep it above 1500 so it doesn't kick thrbinjectors back up.

 

Auto. Not shifting. It stays in gear and just starts to accelerate when at 1500 and decelerating.