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P0172 Bank 1 rich and hard starts after stalling in 4 low

Discussion in '1st Gen. Tacomas (1995-2004)' started by Wulf, Aug 14, 2019.

  1. Aug 14, 2019 at 2:26 PM
    #1
    Wulf

    Wulf [OP] head like a hole

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    Recently I got a P0172 "Bank 1 rich" that comes back as soon as I clear it. I was descending a trail in 4 low and 1st gear and the check engine light came on.

    At the time I was probably at 11k feet in altitude so I initially thought it may have been related to that because I've had the code come up in the past but cleaning the MAF would make it go away for a while. This time if I reset the code the CEL comes back as soon as I start the truck again.

    Aside from loading up the parts cannon with a new MAF and O2 sensor, what should I be looking at? Is it possible I have a leaking injector or some other fuelling issue?

    Other details:
    • 3 years / 23k miles ago I swapped an engine from a 2002 Tacoma into my truck. Supposedly the injectors are slightly larger than the ones that came factory in 1996.
    • Exhaust smells rich/sweet
    • I replaced my O2 sensor about 4 years / 30k miles ago with a Denso one so I have a hard time believing it's the O2 sensor again but maybe I fouled it due to last point
    • If I lug the truck in 4 low and stall the engine it seems to flood out and takes a bit of cranking with foot on the pedal to get it to start again.
     
  2. Aug 14, 2019 at 2:31 PM
    #2
    eon_blue

    eon_blue moist

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    No idea on the code but when my truck stalls out in 4lo it will sometimes take a long time cranking to get it going again, usually I just let it sit for a minute before trying. Kinda irritates the people behind me but I just tell them "manual trans problems" and they usually understand.

    I have heard that a bad/dirty MAF sensor can cause this code just like it can also trigger a P0171 (too lean)...maybe give that a good cleaning and see?
     
  3. Aug 14, 2019 at 2:37 PM
    #3
    Wulf

    Wulf [OP] head like a hole

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    Ah ok, it's reassuring that it's not just me in that regard. I had the MAF off and gave it a good bath in CRC MAF cleaner, filled up the bullet part with the sender wires, dumped it out, repeat a few times, let it dry, and reinstalled it with no luck.


    Aside from the CEL I can't tell that the truck is running particularly different from usual either.
     
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  4. Aug 14, 2019 at 2:44 PM
    #4
    eon_blue

    eon_blue moist

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    I'm sure you've looked this up too but my expert google mechanic skills have brought me to this...

    Screen Shot 2019-08-14 at 2.42.01 PM.jpg


    I guess in order of the list, the O2 sensor wouldn't be too hard to pull out and take a look at

    I would think if the temp sensor or thermostat were malfunctioning you'd probably be seeing overheating on the gauge but maybe not?
     
    Last edited: Aug 14, 2019
  5. Aug 14, 2019 at 2:48 PM
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    eon_blue

    eon_blue moist

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    Chris The Mechanic is online and eager to help too

    Screen Shot 2019-08-14 at 2.45.37 PM.jpg
     
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  6. Aug 14, 2019 at 2:54 PM
    #6
    OneWheelPeel

    OneWheelPeel Well-Known Member

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    I only trust repair feedback from TW and the Dealership
     
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  7. Aug 14, 2019 at 2:57 PM
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    Wulf

    Wulf [OP] head like a hole

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    According to the 3rd gen forum I should threaten to sue the dealer and demand a new truck
     
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  8. Aug 14, 2019 at 2:58 PM
    #8
    Wulf

    Wulf [OP] head like a hole

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    Yeah I guess I can pull the O2 sensor and see what it looks like.


    The spark plugs are only a month or two old, I should recheck all my wire connections though I did that already without any luck.
     
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  9. Aug 14, 2019 at 3:03 PM
    #9
    OneWheelPeel

    OneWheelPeel Well-Known Member

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    Win
     
  10. Aug 14, 2019 at 7:37 PM
    #10
    cruiserguy

    cruiserguy Well-Known Member

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    Haha you're dumb you trust the dealership?! Haha dummy
    I only trust TW :D
     
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  11. Aug 14, 2019 at 7:40 PM
    #11
    cruiserguy

    cruiserguy Well-Known Member

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    On the O2 sensor isn't there a way to test it? Like an ohm spec? That's not a very common DTC, seems I don't see it too often.
     
  12. Aug 14, 2019 at 7:40 PM
    #12
    Wulf

    Wulf [OP] head like a hole

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    Trust TW? I don't even trust myself :luvya:
     
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  13. Aug 14, 2019 at 7:42 PM
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    cruiserguy

    cruiserguy Well-Known Member

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    So when this happened, like it was flooded when you were starting it? Saw or smell that it was rich? Possible injector plugged/gummed up with something that worked it's way out?
     
  14. Aug 14, 2019 at 7:43 PM
    #14
    Wulf

    Wulf [OP] head like a hole

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    In the case where this latest CEL came on I was just idling down a steep grade, the truck didn't even stall or anything. It came on and has been on since
     
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  15. Aug 14, 2019 at 7:47 PM
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    cruiserguy

    cruiserguy Well-Known Member

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    Ohhhhh I see I misunderstood. So yeah, I'd start with clearing it, being that it's nothing obvious and see if it comes back. Sometimes those weird anomalies.... Electronics you know
     
  16. Aug 14, 2019 at 9:29 PM
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    Glamisman

    Glamisman Well-Known Member

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    locate the line from the charcoal canister... probably the size of your little finger, disconnect it from the intake manifold and plug the inlet. Clear the code and see if that helps. There is a possibility that on your decent raw fuel traveled into the canister and is sitting there and is being sucked into the motor. This makes the most sense to me plus its FREE.
     
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