PCV/Hose/Lean Codes Troubleshooting - Now a hiss

[JClark86]

99 Expedition 5.4L

Been searching around for answers (great site, btw) trying to diagnose the 0171 and 0174 codes in the 99 Expedition I just bought.

Picked up a new PCV valve today and installed it, now I'm getting a loud hissing sound from the area. The one I installed is a little different shape/style than the Motorcraft one I removed, but in general its the same part. Is there a gasket or washer or something to seal up the hole in the valve cover better? I just pulled one PCV out and push (dropped) another one in. Is it supposed to be tight? There's a small amount of play and either can be pulled out/dropped in with little resistance.

I plugged the old Motorcraft one back in to see if there is a difference but it does the same thing.

I drove around the block but the CEL is still on, how long does a Ford ECU take to reset? I'm going to go grab the PCV hose next and try that.

Any help is more than welcome.

Thanks,
Jesse

[Twinsdad98]

You need to clear the codes otherwise they will stay in memory. Disconnect the battery for 10 minutes to wipe out the KAM (Keep Alive Memory) and they see if the codes come back. Sounds like you didn't clear the codes out, but just changed the part.

[JClark86]

^^ Thanks, didnt know that. I'll disconnect the battery tonight.

Also found out there's a grommet in by the PCV. Either I didnt see it, or it isnt there. Either way, the hose ($47 wow) and grommet ($8 WOW) should be in by Mon.

[chrisf250-460]

the cel light will go off own its own after 3 drive cycles if the condition no longer exist. did you change just the pvc valve if so check the 90 elbow that goes into the back of the intake,it is bad for rupturing which could cause a hissing sound