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22/04/2021 3:25 pm
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My 1998 F150 5.8 Lariat V8 has is throwing a P0171 Bank 1 lean condition. I have replace both O2 sensors on bank 1, I have replaced the MAF, and replaced my air filter.
Long term fuel trims on bank 1 are at 23% when idle and drops to 17% at 2500 rpm.
Long term fuel trim on bank 2 are at 21% and when idle drops to 16% at 2500 rpm. I used scottys cigar method for smoke testing and have not found any vacuum leaks. I even have tried spraying carb cleaner on the vacuum line to no avail.
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22/04/2021 4:19 pm
If there is no vacuum leaks then maybe you should start diagnosing somewhere in the fuel system. Maybe it could be a weak pump or a fuel pressure regulator not working properly or a clog in the system like a fuel filter.
