I hope this might help some of the others here. I have a 1998 F150 with a 5.4L, and was having an issue with a rough/low/surging idle, and codes P0171 & p0174 displayed on the OBD II scanner I bought. To make a long story short, I replaced one O2 sensor, the IAC motor, and the MAF sensor, all to no avail. As a last ditch effort to fix the truck, I limped it over to an Oreilly's Auto and had one of the guys come out to look at it. I fired it up and noted the rough/low/surging idle, so I opened the hood to show him the engine, I could hear a loud whistle coming from the back of the motor. The Oreilly guy thought it was the IAC motor I put in, so I ran my hand along the IAC motor and found a vacuum line that runs from the PCV to the underside area near the IAC motor had rotted. It broke apart in my hand it was so brittle. I rigged up another vacuum hose setup to the PCV, fired up the truck, and it now purrs like a kitten. I wish I had kept the piece to show every one, but I left it at the store. I drove the truck home and let it sit in the driveway and run, and it never surged nor ran rough, and no codes. If only I had found the hose before I spent the bucks on the other things! Oh well!! I hope this is helpful.

Matt

 

If only you had come here first and SEARCHed on "p0171 P0174" you would have saved hours of time and all of your money spent fixing this extraordinarily common fault.

Steve

 

You know, if I had known this forum existed at the time, I would have done just that. However, seeing as how I just found it, you can certainly understand my wanting to help out fellow Ford fans, only to find out that it is apparently is just an "extraordinarily common fault".

Matt

 

This one????

 

What size hose is that? I need to replace a piece or two on my 97.

 

I didn't go to the stealership and pay for the whole elbow and hose, I went and bought some 3/8 inch radiator tubing for 12 cents and cut it to size. Seems much more solid than the original squishy stuff...