P0171 & P0174

Discussion in 'Performance' started by HiHoeSilver, Oct 22, 2018.

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  1. HiHoeSilver

    HiHoeSilver Away!

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    Sorry for the book here. The past few days have been a good mix of frustration and learning...

    Thursday night I played taxi driver for youth group. I knew I was getting low on fuel. Tank had e85 in it. It was well out of my way to get more and I knew I'd pass it in the morning. Bad idea. Friday morning halfway there.... (trombone sounds). I called my GREAT NEIGHBOR, who brought me his mower can. I'm thinking if it's enough to start it back up, it'll work. 2.5 gallon can, not full. Dumped it in, cranked a good 4-5 times, but did end up starting. Drove 2-3 miles straight to the e85 pump and filled up.

    Friday night, taxi driver for the football game. I get about 2 blocks from the house and the CEL pops up. What?! Get home and the scanner said P0171 & P0174. LTFTs are pegged at 25% limit. Vacuum leak? I do a little checking to no avail. I look at the data some more and see that I can't get the STFTs to pull down, even under WOT. O2s seem to be acting normally. Fuel delivery? Pressure gauge shows 59# at the rail. I clean the MAF (which I did recently). No change.

    Black bear is next weekend. If course, this happens now. Lol. I'm swinging it by my buddy's shop on the way home today. Need to see MAF voltage and alcohol % for starters I think. Will update.

    Questions in the mean time for anybody who actually read this and is smarter than me.

    1. Could I have reset the LTFT somehow myself? (I've read battery disconnect for ..) If so, would that reset the alcohol %, too? I read you shouldn't do that with ethanol in the tank.

    2. Did my little regular gas addition throw this whole thing? Being such a little amount, I'm guessing the truck didn't recognize a refueling event, and ran those couple miles on 87 in the e85 tables... But wouldn't that have caused rich codes instead of lean?

    3. The STFTs get worse under load. Bad MAF? Bad/clogged injectors? Could it really just be a bad tank of E85?
     
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  2. HiHoeSilver

    HiHoeSilver Away!

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    Update even though nobody's here.

    Alcohol % at 20. Tank at <1/4. Tail end of the E85 fill up. There's the lean codes.

    Got a lecture about the poison e85.

    Filled up on 89 (not my preferred brand).

    Reset LTFT and composition %.

    Ride home looks good.

    Phew.
     
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  3. Z28TWITCH

    Z28TWITCH Member

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    Why in the world are you running e85? Have you done something to the engine to command e85? A stock motor with that much octane is going to do some funky things. Your ltft's will be off the charts because you don't have the same volatility of normal pump gas....I'm very interested in whats going on here.
     
  4. HiHoeSilver

    HiHoeSilver Away!

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    It's a vin Z truck. It's perfectly capable of running ethanol.
     
  5. sumo

    sumo dn ʇǝƃ ʇuɐɔ & llǝɟ ı

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    What’s that? Bank 1 and 2 rich? I had that problem. My Maf wasn’t reading right so I pulled it and sure enough I had some crud stuck to the resistor. Cleaned it off and reinstalled. Haven’t had those codes return since
     
  6. HiHoeSilver

    HiHoeSilver Away!

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    Lean.
     
  7. sumo

    sumo dn ʇǝƃ ʇuɐɔ & llǝɟ ı

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    Still could try cleaning maf. Also you can try spraying brake cleaner around hoses, throttle body, base of Intake and see if the engine idle raises or smooths out. That will indicate a leak or you can monitor the ST FUEL TRIM and see if it spikes.
     
  8. HiHoeSilver

    HiHoeSilver Away!

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    Solved. It was the fuel composition issue.
     
  9. Fless

    Fless Full Access Member

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    So what was the solution? Just a higher mix of gasoline, or changing out the Flex Fuel Sensor?
     
  10. HiHoeSilver

    HiHoeSilver Away!

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    06 doesn't have a sensor. It's all algorithm. The solution was to run it empty ,fill with gasoline, and reset the composition with a scanner.
     

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