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Not a vehicle I worked on, but took it upon myself to finish someone's unfinished work to do the job right, the first time.
Info: 2003 Ford F250 4x4 5.4L Gasoline.
Currently replaced: TPS & IAC. Schedule was performed on it recently with new filters and fluids, the works.
Also cleaned throttle body and housing and added Sea Foam to both tank and vacuum line for intake manifold. Checked and found no apparent vacuum leaks (also used brake clean around the vacuum lines.
Problems: -Engine hesitation when the first phases of increased throttle. It bogs down to almost 200-400 rpm before it smooths out.
-Idle issue were after engine is at operating temperature, rpm begins to fluctuate from anywhere to 300-1300 rpm (before any repairs) and now fluctuates around 500-900 rpm (after parts replaced and cleaned).
-Side note: before repairs 1 sometimes 2 (After repairs and tests) store, 0171 and 0172 which is bank 1 and 2 lean.
My notes: I listed out what probably isn't the problem, fuel pump, filter, coil packs, tps, IAC, and vacuum lines. Might of overlooked but with the info I recieved from the previous mechanic and to what I've seen, I'm leaning to the injectors but ultimately the fuel that is used in this isolated location. Pretty sure we have generic octane gasoline and with all the sand and what not around many other vehicles like the Dodge Dokota's have hesitation issues.
So: Lend me your opinions and insights. Thanks in advance
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I would first check the PCV hose assembly. The rubber elbows (especially the one on the rear that connects to the intake) get soft and crack causing a vacuum leak. The other most common problem for those codes is a dirty MAF sensor. Try spraying the filaments with brake parts cleaner or MAF cleaner but do not touch them. they are very fragile.