1998 Ranger XLT 4x4 4.0
Looking for some ideas. Just picked up a Ranger for my kid. When I brought it home it had the P171 and P174 codes. It was leaking oil from the valve covers. So, I replaced the lower intake gasket, injector o-rings and plate gasket, upper intake seals, valve cover gaskets, EGR valve, plugs, wires, air filter, EGR o-ring in upper intake, EGR valve pressure sensor, PCV valve and the PCV hose, and sprayed out the MAF sensor. Upon initial startup, there were no codes and ran very strong. After warming up and taking a short test ride, the P171 and P174 codes returned and the engine idle is sometimes rough...at times sounds like it is ready to stall and then returns to a smooth idle. I have checked and do not notice any vacuum lines broken or collapsed. Any thoughts would be helpful.