P0171 won't go away

Discussion in 'Subaru Legacy' started by Iowackers, Jan 18, 2021.

  1. Iowackers


    Jan 18, 2021
    Likes Received:
    So my sons 2007 Legacy 2.5 non turbo started misfiring about a year ago. Car only has 58,000 miles on it. Engine was rebuilt due to previous owner running it low on oil and spinning a main bearing. Traced misfire to carbon tracking on original plugs. Replaced plugs and wires and all was good for a few months. Then got the wonderful P0171 - Bank 1 Lean. Read up alot on it. Decided to build my own smoke machine to look for intake leaks. Low and behold, massive leak from under air box that attached to throttle body. Removed air box. Someone had put a couple wood screws through box into internal baffle. Guessing it came loose. Problem is they tried a couple other times and apparently missed the internal baffle. Never sealed those holes or the screws they installed. Bought and installed a new air box. Car was code free for a few months. Then P0171 came back on. Cleaned MAF sensor. Code cam back after a few days. Drove car with scanner monitoring parameters. O2 sensor 1 seemed very slow to respond and would stay in the lean range most of the time. Replaced O2 sensor with a new Denso sensor. Light came back on after about 4 weeks. Did smoke test again. Noticed a little smoke coming out of EGR valve where solenoid attaches to valve. Very little smoke, but enough to see it.
    Could this be enough to cause a lean condition? If valve is not open I would think maybe? But I would also think that I would hear an exhaust leak then when EGR was flowing.

    Any suggestions?? Am I missing something here??

    Thanks for any help.

    Last edited: Jan 18, 2021
    Iowackers, Jan 18, 2021
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