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Thread: lean idle at startup

  1. #1
    Tuner in Training blown3qtr's Avatar
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    lean idle at startup

    truck runs lean about 18.0:1 AFR for about 30 sec at startup hot or cold. After 30 sec truck idles +-14.7:1. What tables should I adjust to fix this condition?

    '99 silverado 2500 4x4, 408, inlet forward MP122HH, 60# mototrons, borla exhaust, HPT 2bar OLSD

  2. #2
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    I see you are OLSD, have you checked your histogram #7 to see what ve cell you are during the lean afr readings? it could be that one or two of your ve cells are set to lean since after 30 seconds or so you afr comes back in line, you could now be using a different spot in your ve table. just a guess though....
    2003 Silverado SS -6.0L - 4L65e - AWD
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  3. #3
    Tuner in Training blown3qtr's Avatar
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    Quote Originally Posted by Holty
    I see you are OLSD, have you checked your histogram #7 to see what ve cell you are during the lean afr readings? it could be that one or two of your ve cells are set to lean since after 30 seconds or so you afr comes back in line, you could now be using a different spot in your ve table. just a guess though....
    I'll check that out.

    '99 silverado 2500 4x4, 408, inlet forward MP122HH, 60# mototrons, borla exhaust, HPT 2bar OLSD

  4. #4
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    Turn off your AIR pump and see if that goes away.

  5. #5
    Tuner in Training blown3qtr's Avatar
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    Quote Originally Posted by jimmyblue
    Turn off your AIR pump and see if that goes away.
    No A.I.R.

    '99 silverado 2500 4x4, 408, inlet forward MP122HH, 60# mototrons, borla exhaust, HPT 2bar OLSD

  6. #6
    Tuning Addict WS6FirebirdTA00's Avatar
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    in SD it is typical to see lean hot starts, search and you will see.
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    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  7. #7
    18:1? It RUNS at 18:1?

    16.5 or 17 :1 is pretty much the limit in terms of flamability limits as far as I've ever seen in real life.
    03 Silverado
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  8. #8
    Tuning Addict WS6FirebirdTA00's Avatar
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    it will run
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  9. #9
    Tuner in Training blown3qtr's Avatar
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    runs lean off idle also. not as lean though. 18:1 at idle for 30 sec cold or hot.

    '99 silverado 2500 4x4, 408, inlet forward MP122HH, 60# mototrons, borla exhaust, HPT 2bar OLSD

  10. #10
    Tuning Addict WS6FirebirdTA00's Avatar
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    thats odd it sounds just like the air pump kicking on, yet you dont have one you said
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  11. #11
    Tuner in Training blown3qtr's Avatar
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    Is there some sort of start up or warm up enrichment that could be out of cal?

    '99 silverado 2500 4x4, 408, inlet forward MP122HH, 60# mototrons, borla exhaust, HPT 2bar OLSD

  12. #12
    Tuning Addict WS6FirebirdTA00's Avatar
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    There are table for startup enrichement, but they dont generally cause a lean condition like that for an exact amount of time.
    Sulski Performance Tuning
    2000 WS6 M6 - LS6 (long block, refreshed top end), 10.8:1 CR, 90 mm ported FAST, Exo-Skel, 227/232 cam, QTP HVMC, EWP, GMMG, 9" w/4.11s
    2018 Sierra SLT 5.3L A8 - Airaid intake tube, GM Borla catback, L86 Intake/Ported TB

  13. #13
    Tuner in Training blown3qtr's Avatar
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    ????

    '99 silverado 2500 4x4, 408, inlet forward MP122HH, 60# mototrons, borla exhaust, HPT 2bar OLSD

  14. #14
    ever figure this out?