P0171 and P0174
06-11-2012, 09:33 PM
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P0171 and P0174
I have a 2003 F150 V8 4.6L with the original motor and tranny at 313,000 miles. My service engine soon light came on so I pulled the codes and got P0171 and P0174. I know it has something to do with the intake. The light came back on after I cleared the codes.
It has been running fine until today when started to stall when I would be at a complete stop. You can hear it struggling and then it will completely die. I replaced the air filter about 1,000 miles ago. If anyone could shed some light on what it might be or what I should check for that would be great.
It has been running fine until today when started to stall when I would be at a complete stop. You can hear it struggling and then it will completely die. I replaced the air filter about 1,000 miles ago. If anyone could shed some light on what it might be or what I should check for that would be great.
06-12-2012, 09:38 AM
#4
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More than likely a vacuum leak. It would be something common to both banks. I'd check all hoses including the engine's air intake ducts.
Low fuel pressure can also cause this. So can a lazy MAF sensor.
Low fuel pressure can also cause this. So can a lazy MAF sensor.
06-12-2012, 01:50 PM
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^ +1. If it's bad (or high) at startup, also check the IAC valve at the throttle body. Most common source of a leak (especially in the 5.4) is the hose behind the throttle body that wraps around to the PCV valve on the valve cover. At the bend of that hose, it tends to collapse, and develop a hole. There have been multiple threads on this forum, for those chasing the same ghost.
06-12-2012, 04:30 PM
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I pulled off the boot of the pcv tube and it seemed fine. I do hear a slight hissing coming from around the left side of the engine (opposite of the intake) towards the back of the fuel rail.
06-12-2012, 08:08 PM
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Ok so the hissing sound seems to be coming from what I believe is the pcv tube. The tube that the arrow in the picture is pointing too farthest to the left. It seems to be further up the tube towards the back of the engine. Anyone have any directions on how to replace it. I'm kind of a newb at this stuff but if given directions I'm sure I can do it.
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06-12-2012, 08:54 PM
#8
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^ +1. If it's bad (or high) at startup, also check the IAC valve at the throttle body. Most common source of a leak (especially in the 5.4) is the hose behind the throttle body that wraps around to the PCV valve on the valve cover. At the bend of that hose, it tends to collapse, and develop a hole. There have been multiple threads on this forum, for those chasing the same ghost.
