Hello All, I have a 1996 F-150 4.9L EFI 2WD 5 SPEED. I’m ready to give up here, four years of the infamous DTC P0174, I replaced all three O2 sensors, replaced EGR valve and mechanism near it, I even welded to repair holes in the skinny heat tubes for the egr sensor, cleaned the MAF, replaced both fuel pumps, replaced fuel filter, set timing, used starting fluid sprayed in all vacuum type areas safely while engine running, result was no vacuum leaks. Next I’m trying an additive with the hope that either an injector or carbon on the valve seats are causing the too lean DTC. Any reply would be greatly appreciated. Thanks.<?xml:namespace prefix = o ns = "urn:schemas-microsoft-comfficeffice" /><o></o>
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How many miles are on it?

I have the same year and engine with 221,000 and just recently had to have the head rebuilt. Was chasing a miss, and it failed a leakdown test even though compression test was fine. It might not be the typical place to look, but if you think it might be carbon on the valves, it might be worth a shot. My exhaust seats in 2 and 3 were so worn, they sat 1/16' below the rest of the valves in the head.