Engine Performance problem
1994 Ford Aerostar 6 cyl All Wheel Drive Automatic 167 miles

This is a 4.o litre.recently started running rough.not as bad when cold but as it comes up to operating temp the engine light comes on and it starts to run very rough and stalls when you come to a stop and try to idle.plugs are fairly new and look normal.recent scan reported problem with one bank.very dark rich looking deposits in the end of tailpipe.have had to replace one of the spark plugs about every six months due to fouling not sure if this is related to current problem.local mechanic that did scan thinks possible injecter problem.using fuel like crazy too up until it started running too rough to drive.