1994 E-150 Conversion van idles rough in park
 

I have a van that stalls occasionally when it is First started and tries to stall again initially. After I get it moving it almost runs normally except when it stutters(loses power) 3 or 4 times in intervals. It can maintain highway speeds even with the hiccups. When I put it in park,it idles high and rattles badly . The Check Engine light comes on while waiting at the light and during idling but goes out while drive on. Does anyone have any idea what is going on?:eek: