00 4wd v6 dying while driving

My check engine light came on and I took it in and the came back with a code of PO440 - Evap control system malfunction. They told me it was the gas cap, ok fine, I went on my merry way, however when i am driving it just dies, could be doing 60 or 30 mph, does not matter, I slip it into N and restart it, never a problem.. Check engine light does not come back on.. Does anybody have any ideas...