Had a question for the knowledgeable folks on here. I recently picked up a new to me '15 Ecoboost Lariat and noticed something when using my cruise control. I had it in sport mode today to do a little spirited driving to get on the highway. Upon exiting I decelerated to 45 again initializing the cruise control. When I went to brake coming up on a light, the truck seemed to.. hard to explain.. jolt and slow down as I applied the brake? I assumed maybe it was just sport mode dropping gear when I hit the brake but it was a very noticeable jolt. I recently took it on a trip out of town and never noticed it do that outside of sport mode. It happened one other time while using cruise in sport mode. I'm familiar with the downshift lurch as I had a PRX tune on my 13 F150 5.0 and it liked to drop gear whenever it could to give me more power. This was more jarring I would say than that. Just curious if anyone had any ideas. I don't believe I will be making it any sort of habit driving or cruising in sport mode but since I jut got the truck if it's something I need the stealership to look at I would like to know. Thanks in advance!!

 

After looking into it more it might be the engine braking that is activated in sport mode but it seems to be pretty aggressive when slightly letting off the throttle. Not sure if that is normal or not as this is my first truck with this feature.

 

It will do the same thing in Tow/Haul mode, it uses engine braking to slow down. My 2013 seems to drop a gear every time I hit the brakes even slightly and both the 2016 F650 and 2020 F750 at work are even more aggressive.

 

Every now and then mine will either jolt, as you said, upon braking, or have an unexpected extra boost of power on accelerating from low speed or a stop. It doesn't seem to have anything to do with cruise control; more like there's just a software lag.

 

Thanks for the replies guys, just making sure since this is my first ecoboost truck. Not to hijack my own thread here but do you guys also have a little vibration in the floorboard running 4a? Never owned a 4 wheel drive either lol last truck was a 4x2.

 

Vibration and noises should be expected when in 4a/4wd.

 

Thanks for the help, I kind of assumed so but figured I'd ask. Really appreciate you guys and looking forward to this ecoboost!