I have a 1997 Ford Explorer which has a rough idle.I have had a new engine fitted but it still idles at around 500rpm and will sometimes stall when i go to pull away.There is no CEL on at all,i have replaced the IAC and cleaned the MAF,replaced the air filter, TPS sensor,Plugs and leads.I was wondering if it was the PCV or EGR valve.This happens to the truck when its hot or cold,so im not sure what the hell's going on. If anyones got any ideas i would be very grateful.