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Ron, ASE Certified Technician
Category: Ford
Satisfied Customers: 35487
Experience:  23 years with Ford specializing in drivability and electrical and AC. Ford certs and ASE Certs
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I Have a Ford pickup that runs gh idle and then down about 3

Customer Question

I Have a Ford pickup that runs high idle and then down about 3 to 4 hundred rpms difference. Does it mostly when its cold. It had a 2 codes PO171 and Po 174 so we changed the Air Flow Sensor out and it didn't help so we checked for vacuum leaks in intake and vacuum lines. do you have any suggestions?
Thanks Eddie
Submitted: 1 year ago.
Category: Ford
Expert:  Ron replied 1 year ago.

Hello Eddie and thank you for your question,

What year is your Pickup and what size engine are you working on?

Customer: replied 1 year ago.
Thanks Ron for helping us out on this. It is a 2001 F150*****with a 5.4
Expert:  Ron replied 1 year ago.

The codes P0171 and P0174 are lean code and in 99% of all cases on your 5.4 they are set due to an engine vacuum leak and on this engine it is usually caused by a rotted out PCV supply line nipple. Its hard to see because of its location. Locate the PCV valve in the passenger side valve cover and take your hand and follow the supply line from the PCV around to the back side of the intake where it connects and check the rubber nipple to see if its rotted out and leaking. In most cases it will be. Check this and let me know the results and we can work from there there if need be.