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Thread: 25% ltft

  1. #11
    Lifetime Member 5.7ute's Avatar
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    All good.
    The tune itself cannot change, but there are a few learned values that can mess with you. Disconnecting the battery should reset these, as will reflashing the tune.
    The Tremor at AIR

  2. #12
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    OK great. That was my first mistake, I didn't save the tune before I started the engine. But by disconnecting battery, which I do all the time, and clearing fuel trims, then reflash, and it still starts running rough and popping right away should be saying the tune isnt the problem. Am I correct saying that?

  3. #13
    Lifetime Member 5.7ute's Avatar
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    That is how I would see it, yes.
    The actual tune file does not get modified while the engine is running. There is just a few learned values that get stored elsewhere in the PCM's memory. So the file you read out of the pcm will be the exact same file you flashed in. Sometimes there are a few minor variances due to the way efilive, (or any other software), converts the binary value to usable units but that is another story for another day.
    I would be trying to isolate the cylinder causing the miss and swapping components around to isolate the cause.
    The Tremor at AIR

  4. #14
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    Good deal. Thanks a lot for hanging with me here tonight.
    Hopefully I'll update soon with what i've found.
    Again, really appreciate your help.

  5. #15
    Lifetime Member 5.7ute's Avatar
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    No worries.
    Daytime over here.
    The Tremor at AIR

  6. #16
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    Ah right

  7. #17
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    So I had checked my fuel pressure to be sure and all seems well except when I pulled the guage off the rail I noticed how yellow looking the gas is. Some dripped on the floor, and even on concrete it still looks yellow. This was 93 octane I bought at a very busy location.
    So i dripped a little bit of 87 octane for my mower on the floor. If you look closely, you can see the yellow at the top of the picture and the clear gas actually making that partial ring as it flows in to the yellow. WTH is the yellow? old gas still in the tank or just bad new gas. I'm 99% sure I completely emptied the tank years ago when I put the new 255lph pump in. I haven't put any new gas in till this start-up.

    Is this my severe miss and backfiring?

    Click image for larger version. 

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  8. #18
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    Guys, thanks for trying to help me out. I really appreciate it. Even tho my problem wasn't in the tune, it helped me to work towards finding the problem.
    I'm new here but will be visiting often as I try to learn how to work on these tunes.
    Long story short, my bank 2 coil harness was reversed. DOH!

  9. #19
    Lifetime Member 5.7ute's Avatar
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    Quote Originally Posted by KCG View Post
    Guys, thanks for trying to help me out. I really appreciate it. Even tho my problem wasn't in the tune, it helped me to work towards finding the problem.
    I'm new here but will be visiting often as I try to learn how to work on these tunes.
    Long story short, my bank 2 coil harness was reversed. DOH!
    Thanks for the update.
    The Tremor at AIR

  10. #20
    Joe (Moderator) joecar's Avatar
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    I was away for a few days, what did I miss...?

    Bank2 coil harness was reversed: so the cylinders were reversed...?

    Fuel containing yellow substance: what is that...?

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