tidenbucks

New here and basically just looking for opinions about what may have caused a problem. One evening last week I noticed that my engine was idleing rough while but only when in gear and stopped. While moving it was fine. I had filled up with gas the day before and thought maybe it had a little water or something in it. The next morning it was running fine while driving to work, but twice it felt like the motor "surged" slightly. After the second "surge" the service engine light came on but the truck was still running fine...good oil pressure, not running hot, etc. I arrived at work and was backing in to my parking space and had to stop and pull forward to get properly aligned. As soon as I put the vehicle in drive, the motor surged again, but it was like stomping on the accelerator this time and the truck shot forward. I was sitting 10 feet away from a guard rail that was designed to stop 18 wheelers so the end result was not pretty. The body repair is being doen at a Ford dealer and they have been instructed to diagnose and repair the mechanical problem as well, but I am just looking for opinions on what the cause could have been. My apologies for being so long with this, and my thanks for any responses.