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Working on my cousins F-150 and it has me stumped. It is a 2002 F-150, 5.4 V8, 4X4.
First off it is getting a couple of codes occasionally. The codes are P0171 & P0174, if I remember correctly, they are for lean bank 1&2. Also when at idle or sitting at a stop sign/light it occasionally has a really low idle and sounds like it was to shut off. Finally the 4x4 system is not working. I know the transfer case does engage, but the axle shafts do not. The vaccuum actuator does more in and out when the switch is activated/deactivated. The seal on the outer end of the passengers side axle tube was leaking and had to be replaced so the axle tube was off. As far as I know everything got reassembled correctly.
Is there anything that ties these things together? Any ideas on where to start?
Address the codes 171/174 and your idle issue will go away.
Look at the rubber ELL behind the vertical intake riser.
If the front actuator operates and does not lock the left front axle, the Yoke is broke that move the splined collar inside the housing.
Nothing is out of the ordinary, just repair for the issues.
Good luck.
Thanks for the response! I am not familiar with the rubber ELL. What is this item? Is this a likely cause of the codes?
The infamous PCV hose elbow, around the back, connects the PCV valve to the back of the intake. Check the complete PCV hose, it's an extremely common issue.
then look at all the other vacuum hoses... two small 1/4 inch about 8 inches long above the left valve cover on the EGR system are CLOSE to exhaust system piping and can get hard / burn/ crack.. take each hose off one at a time, examine and replace any that are not flexible.