I think you have two issues. First, you should have a CVT transmission in that vehicle. What happens is, the steel belt inside the transmission begins to slip and you get a hesitation. More than likely this is your issue and the only real way to fix it is to replace the transmission. Some people will rebuild them but the cost is almost the same these days so I would just replace it and get the warranty that comes along with a new unit.
As for the stalling at highway speeds, do you have any codes? You may not have any yet but the common failure on these World Engines is the crank sensor fails and when the PCM is not getting any signal from the crank, it cuts the engine off. You will need to replace the crank sensor.
However, when you replace it you must perform a procedure called an adaptive numerator relearn. Basically, this is teaching the PCM that there is a new sensor. On these PCMs, the only way to do that is with a scan tool that can perform this procedure. It includes a drive procedure specific to this process and the scan tool must be hooked up while doing it. If you do not do this, then you will get multiple cylinder misfire codes and it will cause you many headaches trying to diagnose these misfires because no matter what you do they will not go away until this is performed.
Let me know if you have questions and we can go from there. Thanks
Images (Click to enlarge)
Monday, August 26th, 2019 AT 1:42 PM