Adaptive Cruise Control problems of the 2017 Toyota Corolla

I had to drive around 600 miles to and from family funeral. As others have reported the cruise control on a down hill slope goes out of control. As I reached the top of a hill and started down the cruise control would accelerate to 4000 rpm ( it is really loud) the speed would start increasing and go 15-20 mph over what the cruise control speed was set at. I had to turn off the cruise control to regain control over the speed. I was afraid that something might happen if I did not. Where it seemed my car should down shift it was not. Something is wrong with the programming of the cruise control. This should not happen on a decline. Also, at one point when I was in the left lane and a car passed me on the right, my car slowed down really quickly. If someone had been behind me it could have caused a serious accident. This is my fourth Toyota and I have never had these problems before.

When the cruise control is set and I go down hill my car increases the speed by 8 mph faster than the set speed. My car also makes a loud grinding noise when it does this. I spoke with different Toyota auto employees and some say that the increase in speed and noise are normal and others say the opposite. I have been in many cars driving with cruise control on and never experienced this.