Thanks, IC. Raining here today so I can't do much but am now leaning towards the IAC valve on the throttle body. Van starts and idles in park/neutral fine. Put it in reverse or drive and the idle drops 500 rpm and "chugs" . This is when the code is set. Engine revs fine and no black smoke or soot out the exhaust. So, looks like I'll take the throttle body off and give it a good cleaning before throwing any parts at it.