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Long Term Fuel Trims S/C

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  • Long Term Fuel Trims S/C

    I'm getting occasional rich codes for both banks. When I go in and look at the Long Term Fuel Trims (LTFT), they are -25%, both banks. I'm guessing that may be also be why on my wideband sensor I'm occasionally seeing wide fluctuations in the readings when cruising at steady speeds Closed Loop (CL). They will go from 10 to 18 and I'll have a slight loss of power at both extremes. This doesn't happen every drive though. I don't recall what the maximum ability of the ECU is to pull/add fuel is, but memory suggests that -/+ 25-30% is about it. I can't help but wonder if the ECU is being taxed and under some circumstances it isn't able to keep the Air/Fuel Ratio (AFR) within parameters set elsewhere in the the tune for CL operation.

    My usage elevation varies from 4k to 11k feet, so I expect that there is going to be some pulling of fuel in comparison to vehicles typically used at lower elevation, most of the rest of the country. 90% of my driving is happening at about 8k feet, so I thought that it might be better to try to see if I can get my LTFTs to be closer to 0% at 8k feet to see if that squelches the rich codes and is more applicable to my usage environment.

    I've been looking at the S/C tuning guide knowing that it's still likely to be further updated to jive with the software updates to try to determine the map(s) that need to be tweaked. The best that I can come up with is the map titled Mass Airflow - MAF Sensor Scaling Frequency based on the text in the guide that reads "This can be used to correct fuel trims when your MAF reading / fuel trims are off".

    I'm currently using an unaltered Tune Pack file for my ECU. I've gone through several other tunes for my ECU including the original N/A file to look at that particular map to try to see how they might be different. I've tried to trigger the "compare bins" function to highlight Mass Air Flow map differences between the tunes, but seem to be having a brain fart. They are all the same so I don't know if I'm on the right path to try to sort the the seemingly extreme negative LTFTs. I haven't found any intake/exhaust leaks, and the filter and MAF are clean. The intake itself is the "stock" S/C TRD intake.


    I can't think of what other relevant information might be applicable, so....thoughts or ideas and feedback?
    2011 RCSB S/C'd 5.7L AWD Tundra
    Tesla > Edison

  • #2
    Is this the MAF that has to be tuned for CAI too?

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    • #3
      Originally posted by Frank View Post
      Is this the MAF that has to be tuned for CAI too?
      I'm not sure what MAF that you're asking about. This has the factory MAF with the TRD CAI that comes with the S/C. From what I've read, the MAF settings are indeed changed by some owners, but I don't know which maps those are. Kinda why I posted.
      2011 RCSB S/C'd 5.7L AWD Tundra
      Tesla > Edison

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      • #4
        So long and short fuel trims can be corrected in thise Hz vs g/Sec table????

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        • #5
          It might be helpful if you could give the name of the table to which you're referring. With that said, I have been so busy at work that I haven't even been able to drive my truck, so this has become temporarily idle.
          2011 RCSB S/C'd 5.7L AWD Tundra
          Tesla > Edison

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          • #6
            I was refering to thing
            Attached Files

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