Ford E-350 - surges forward, stalls
My van has been acting strange. I will be driving along, and the sound of the engine will suddenly change, as if I had pushed on the accelerator. Sometimes the van jumps forward, and I have to take my foot completely off the pedal to prevent it from racing out of control. Other times, it will just sound like (increasing RPMs) like I had pushed the pedal down to 'race' the engine a bit.
Other times, what sounds like 'the opposite' of the above happens, but I don't know how to describe it very well. When this happens, I think its 'about to stall' because a few of the times it did stall, acting like I was out of fuel. (Both times, cranking the starter (longer than usual) was all it took to get her running again.) When this happens, I try to go home or pull over and wait - because it seems like if I drive it too long like that, it is more likely to stall.
If I wait a few hours or over-night before driving it again, its usually okay again.
Does anyone have any thoughts on what is causing this?