This problem seems to be random. When in reverse, taking foot of brake will sometimes make it go foreword. When in drive taking foot of brake will sometimes make it go backward. Especially when on a slight slanted grade. Sometimes pushing gas and van doesn't want to move. After a hesitation will serge foreword, or backward, depending on gear. Just had the main computer chip or board replaced. Sorry I don't know the name of it. I was told this controlled almost everything in van and was the problem, but it hasn't fixed it. Has anyone else experienced this? I don't know if this is relevant or not, but I have used this van to tow a trailer that is 3200 lbs empty. So, it is probably close to 4200 lbs when I tow it.