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.
The 4.0 SOHC doesn't have a PCV valve. I am having a simillar problem with my 97 4.0 SOHC. On a cold morning, it does not want to idle until it warms up. After that, she runs great. Was told it might be the coolant temp sensor that runs to the computer, (it has 2, 1 for dash gauge, & 1 for computer) haven't tried yet, but will post when I do. Hope this helps u out a little b4 u think about a new MAF ($100.00).
The 4.0 SOHC PCV valve is at the back of the intake manifold. You can see it and feel it from the passenger's side of the engine. It has 2 hoses with a TEE going to it.
Like MisterCMK said the most common cause of a 4.0 SOHC idling rough and stalling, especially cold, is bad intake gaskets. I've replaced lots of them.