Sounds like a EGR or Purge valve is sticking open.
The codes would be a big help here.
The KOEO test will not be much help here but the KOER and CM codes would.
The CM codes will not help if you unhooked the battery after you had the problems.

KOEO = Key On Engine Off
CM = Continues Memory
KOER = Key On Engine Running

 

The van does not seem to stall that much anymore but now when I am driving at a steady speed it seems to jerk a bit like it is missing. It is fine and smooth at idle. When I first got the van last week it did this at about 25 MPH. Now it does it all the time. Well at least for my drive home.
Any Ideas?
Thanks

 

Throttle position sensor problem?