I have a 1999 Astro work van. Recently it has a inconsistent problem. I think it is more likely to happen up hill or when I get around 45/50 miles an hour. It feels like someone slammed on the breaks, it sends the fuel gauge flying back and forth, the engine lights go on as if it was being started, and throws me forward like it slammed into something. It may do this once, it may do it over and over again. If it does it over and over again, eventually the Antilock light will stay on. The radio does not turn off during this time. If I turn it off, and let it set it is fine to drive for a while. Since I don’t do much freeway driving and mostly in my small town I don’t get it above 30 often and the problem seems to be gone for a while. I did check the breaks, the break fluid, and none of the idiot lights come on at any other time. The breaks seem to work fine, even when this happens and applying them seems to do nothing positive or negative. I have slipped the car into neutral, and the engine will rev without hesitation, and it seems to stop the problem. I am afraid to experiment too much as I don’t want the engine dropping to the ground.