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  1. #1
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    1997 Chevy Astro LQ4 4L80

    1997 Chevy Astro LQ4 Swap, Low Power

    I swap a 03 LQ4 4L80E NP262 into my 97 Astro 5 years and since then i been trying to figured out why it has no power at WOT. Cant seem to find a right answer on fuel pressure. ive tried different FPR no change, New Pump no change, New fuel rail and fuel filter and 25lb injectors still nothing.



    This video you can hear it bog down



  2. #2
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/ mods, 00 FBVert

    Has it been tune? (Tuned for the transmission?)

    LQ4's have 50 psi so it looks good.

    I see 25lb injectors are the stock injector for LQ4's. Have they been tested or are they new?


    Could be that you have a vacuum leak.

  3. #3
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    1997 Chevy Astro LQ4 4L80

    Stock tune, with trans pressure up'd and torque management disabled. New injectors all been flow matched, no vac leaks

  4. #4
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/ mods, 00 FBVert

    Compression check?


    Any codes popping up?

  5. #5
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    1997 Chevy Astro LQ4 4L80

    no codes, ill check comp, whats the range it should be around

  6. #6
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/ mods, 00 FBVert

    should be around 180 psi.

    More importantly is that they all should be within 10-15 psi.

  7. #7
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    1997 Chevy Astro LQ4 4L80

    Every Cly was 150

    oi67.tinypic.com/2mmhhr7.jpg

  8. #8
    Veteran pajeff02's Avatar
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    '02 WS.6 / '07 Suburban

    Any spark knock or other signs of it leaning out? Have you check the color on the plugs? What does the fuel pressure read under load?

  9. #9
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    1997 Chevy Astro LQ4 4L80

    0 kr, pic in my last post, 65psi at wot

  10. #10
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
    98 T/A w/ mods, 00 FBVert

    How many total miles on the LQ4?

    Cyl pressure kinda low, but good news is they are all the same. Try a wet reading next. Squirt a little oil in through the spark plug hole, turn motor over a few times and then see if the pressure rises.



    I've listen to the bottom video again and I'm not hearing anything, seems like it's healthy.



    Could it be in the tune or transmission? Shift points not quite right....

  11. #11
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    1997 Chevy Astro LQ4 4L80

    Shift points were up'd too, I'll try wet, about 400k on the motor and trans.

  12. #12
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
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    400k.... :wow: Has it had a rebuild?

  13. #13
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    1997 Chevy Astro LQ4 4L80

    Nope not yet, all original besides being swapped from my truck to van

  14. #14
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
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    I'm amazed you have compression......I'm willing to bet it's time for some new rings and at least a line hone, if not flat out a mild bore like .005"

  15. #15
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    I've gone to 600k and still had comp, when I had the heads off to fix a valve you could still see the cross etching

  16. #16
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    1997 Chevy Astro LQ4 4L80

    I think I'm finally getting somewhere, after last night letting it idle and watching sensors I noticed the map sensor didn't really change even after raving it. So I unplugged it and let it use the default settings for it and now when I get on, it takes off. So gonna order a new map, crank, and cam sensors all are still original

  17. #17
    Veteran pajeff02's Avatar
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    Strange that it wasn't setting a code. If the MAP sensor is reading out of range the PCM will usually detect that and set a fault code.

  18. #18
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    1997 Chevy Astro LQ4 4L80

    Sometimes, I've seen alot that don't till the finally fail

  19. #19
    Spaz is My Mentor SMWS6TA's Avatar
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    Navy Blue Metallic
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    Glad you think you found it. I was about to suggest checking the sensors.

  20. #20
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    1997 Chevy Astro LQ4 4L80

    I'm hoping, this has bugging me for years and never been able to narrow it down

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