P0171 and P0174

Tiny
DANAUTHIER
  • MECHANIC
  • 156 POSTS
Your trouble codes p0171 & p0174 are for the fuel system too lean on bank 1 (p0171) and bank 2 (p0174), would say it sounds like a fuel deliery problem.
Check for a restriction in the fuel system. Have your changed your fuel filter lately? Also check fuel pressure, should be 35-45 psi for your vehicle.
Just a few ideas to start with, let me know if this helps or you have any other questions.
Thank you,
Dan
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Monday, December 21st, 2020 AT 1:47 PM (Merged)
Tiny
MAP1995
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Yes, it fuel filter is changed recently. Spark plugs, cables, engine oil, air fuel/gas, oil filters changed few days back.
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Monday, December 21st, 2020 AT 1:47 PM (Merged)
Tiny
DANAUTHIER
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Good to hear you are keeping up on the maintenance. Check the fuel pressure, low fuel pressure will give you the symptoms you describe. If you do not have a fuel pressure tester most parts stores like AutoZone, Advance, etc have a tool rental program.
A restriction in the fuel system will also present like this, look for kinked lines, hoses or a damaged fuel rail.
Clogged fuel injectors are also a possiblity, but they usually do not clog all at once and ususally give you a miss fire code (generally cylinder specific)
also check the fuel pressure regulator.
It still sounds fuel related to me but one other possibility is the PCM is recieving signals from the oxygen sensors that the system is running lean so it is sending more fuel to the engine than it needs. It would give you a very sluggish acceleration and poor idle because the engine would be operating "flooded".
Symptoms of this would be a drop in fuel economy and if very severe the oil may have a fuel smell and the plugs, when pulled, would have a black appearance and a raw fuel smell. Normally the system would catch this & give you an oxygen sensor code but have seen it happen without the o2 failure code. It ended up being corrupted data in the PCM. Not saying this is your problem but if all the above fuel issues come back ok, this would be the next step I would take.
A lot of info, I put it in order of probability.
Let me know if it helps or you have any questions.
Dan
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Monday, December 21st, 2020 AT 1:47 PM (Merged)
Tiny
ASEIBT
  • MEMBER
  • 2 POSTS
  • 1996 FORD EXPLORER
Engine Performance problem
1996 Ford Explorer 6 cyl Four Wheel Drive Automatic 119K miles

I tested the DTC codes and found that I have a P0171 System Too Lean situation. The rest of the data is Fuel System = Closed Loop, Calculated Load 21.9%, STFT Bank 1 = 21%, STFT Bank 2 = 18.7%, RPM 768.
I replaced the left head and gaskets last December. Would this be a bad sensor or something wrong with the fuel rail? Possible vacuum leak? Not sure where to go from here. Thanks for the help.
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Monday, December 21st, 2020 AT 1:47 PM (Merged)
Tiny
LEGITIMATE007
  • MECHANIC
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Yes I would check for a vacuum leak, it doesnt seem like too big of a difference in the readings but big enough to trigger a code, which indicates a possible vacuum leak, also check that o2 sensor on bank one, could be a little weak causing a false code.
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Monday, December 21st, 2020 AT 1:47 PM (Merged)
Tiny
ASEIBT
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I found the green o-ring crushed inbetween the upper intake and an exhaust tube that connects to the header. Its about $7.00 for a new one.
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Monday, December 21st, 2020 AT 1:47 PM (Merged)
Tiny
LEGITIMATE007
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Wow, awesome. Have a good one. Thanx for writing
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Monday, December 21st, 2020 AT 1:47 PM (Merged)

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