A couple of months ago I took my Jetta into a shop to find out why the check engine light came on. They told me it was the thermostat sensor and that was it. I ordered the part but have not put it in yet. Since then my light has came back on. It is acting more and more different and no one knows why. First thing it did was act like the tranny was slipping. Very violent jerks! Only did that for one day. Then the other day I started it up and let it idol. It was about 700rpms normal idol until it reved itself up to about 2500rpms.. A couple of weeks ago I had the cruise control set but not on, when it turned itself on. I was in a 35mph zone when it kicked tried going 65mph by itself. It is like my car is haunted!! I don't know what is going on with it! Can anyone help?!