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  1. #1
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    Default Need to get educated on Holley HP EFI

    Hello! First off, I have reviewed several posts, but I am just not for sure what it is that I am looking for! So, here is what I have...
    LQ4
    L92 Heads
    TFS 30602003 Cam
    Truck Intake Manifold
    90mm Throttle Body
    Headers
    TKO 600
    Holley HP EFI
    Base tune was the 480hp LS2 off of the global



    If you need more specific info, let me know and I will get it.
    The problem... Will not idle after any kind of throttle. We can get it to idle well at 1050 RPM, starts easy and the throttle response is very good. Unfortunately, after any kind of acceleration/throttle it goes right by idle RPM and dies. I am not sure what I am chasing down...I have read so much about TPS, IAC and air/fuel ratio that my head is spinning! It's so close to being driveable, but I just don't know enough about the EFI/ECU/LSx world. Please let me know what info you need and thanks in advance for any help you can provide!
    Matt


  2. #2
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    Default Need to get educated on Holley HP EFI

    What is your IAC hold position and the associated ramp decay time? Also, don't put too large of a number in the "rpm above idle to resume idle control" or that can cause a problem. Lastly, what is your IAC positron % at idle?

    Thanks!

  3. #3
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    What IAC stepper motor are you using? On a previous car, my IAC was wired incorrectly, and the ECU could not control it. While unlikely, it's one thing to verify before digging too far into the programming.
    Bryan (a.k.a. Carbuff)

    70 Camaro RS Hunk'o'Metal - Previous Project
    71 Firebird Project T.O.W. - New Project

  4. #4
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    With the electronically controlled TB there is no IAC stepper. The main TB is opened and closed to accommodate air requirements.

  5. #5
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    The IAC position at idle right now is 5% and not sure of the ramp delay...will check and update. The base tune of 480 hp off global was updated to correct all the sensors like 58X to 24X and cam postition to 1x and the knock sensors. The IAC is the standard/stock replacement for a '01 Chevy truck. Should I be running a different part #?

  6. #6
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    Quote Originally Posted by Rhino View Post
    With the electronically controlled TB there is no IAC stepper. The main TB is opened and closed to accommodate air requirements.
    So, mine is just an IAC, not stepper correct? Not sure if it matters, but the TB is mechanically attached to the pedal.

  7. #7
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    You said you can get it to idle ok. If you adjust your requested idle speed, does this happen as you expect? In other words, is the IAC working correctly at idle? If so, then at least you know the IAC is wired ok... On my car at the moment, which I haven't tuned, there was a parameter on the Idle Settings screen for Hold Time and Decay Time. My default program had about 5 seconds for 'hold time' I think, and when you let off the throttle, it takes a few seconds before it starts to drop. Experiment with those settings and see if it changes the behavior when you let off the idle.

    I'm nowhere close to an expert with this system yet, just throwing out places to experiment that may start pointing you in the right direction...
    Bryan (a.k.a. Carbuff)

    70 Camaro RS Hunk'o'Metal - Previous Project
    71 Firebird Project T.O.W. - New Project

  8. #8
    Join Date
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    Best way to check IAC operation is to go to the target Idle RPM map. With the engine running, click, and drag the target rpm up/down to see if the engine raises/lowers rpm. When doing so, the IAC will open/close to try and achieve the target RPM speed. Providing it is working correctly, I would increase the IAC hold position and decay time to keep the engine from stalling after giving it throttle.
    No longer working at Holley

  9. #9
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    Thank you all for the quick replies! The IAC responds correctly according to the way Derek@Holley said to check it. So, here are some other areas that were in question...the ramp decay is 0.6 seconds and the hold is 10%. How far is this off from everyone else?? I won't have a chance to run it for a couple of days, but I would definitely like to be smarter about it when I do.

  10. #10
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    Quote Originally Posted by burg54 View Post
    Thank you all for the quick replies! The IAC responds correctly according to the way Derek@Holley said to check it. So, here are some other areas that were in question...the ramp decay is 0.6 seconds and the hold is 10%. How far is this off from everyone else?? I won't have a chance to run it for a couple of days, but I would definitely like to be smarter about it when I do.
    Try 30% with a 4 second decay.
    No longer working at Holley

  11. #11
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    Quote Originally Posted by burg54 View Post
    So, mine is just an IAC, not stepper correct? Not sure if it matters, but the TB is mechanically attached to the pedal.
    Sorry for the confusion you do have an IAC with a stepper. When I saw all the truck components I had expected you kept with the same style throttle body. All of my experiences with LQ4's have been Electronic Throttle Body.

  12. #12
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    Default Need to get educated on Holley HP EFI

    Mine has a 25% hold with a 6 second ramp decay time. Just be careful that your hold position doesn't result in an RPM that exceeds your "RPM above idle to begin ramp" or your idle speed can hang up high.

    Also, I like to keep a low number in the "RPM above idle to resume idle control" because this is the RPM at which the ramp ends, and if that point is substantially above the idle speed the idle will rapidly fall to (and often passed) your target idle speed.

  13. #13
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    Quote Originally Posted by Red67Mustang View Post
    Mine has a 25% hold with a 6 second ramp decay time. Just be careful that your hold position doesn't result in an RPM that exceeds your "RPM above idle to begin ramp" or your idle speed can hang up high.

    Also, I like to keep a low number in the "RPM above idle to resume idle control" because this is the RPM at which the ramp ends, and if that point is substantially above the idle speed the idle will rapidly fall to (and often passed) your target idle speed.
    Okay, that was the problem today... couldn't get the RPM down. When we adjusted the "hold" down, it would die. Are there any screen snapshots that show what other folks are running??

  14. #14
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    Default Need to get educated on Holley HP EFI

    For starters, raise the "rpm above idle to start ramp" to its maximum setting then lower the hold position until the idle doesn't hang up high. You can check the IAC position at the resulting rpm to verify where the hold position should be.

    In other words if the "rpm above idle to start ramp" is 1,000 and target idle speed is 800... Then go to your idle speed chart and temporarily bring the target idle to 1800 and see what the IAC position % is... Your IAC Hold Position will need to be less than that % for your idle to return.

    Once you've got it working and understand the relationships you can fine tune for preference.

  15. #15
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    Quote Originally Posted by Red67Mustang View Post
    For starters, raise the "rpm above idle to start ramp" to its maximum setting then lower the hold position until the idle doesn't hang up high. You can check the IAC position at the resulting rpm to verify where the hold position should be.

    In other words if the "rpm above idle to start ramp" is 1,000 and target idle speed is 800... Then go to your idle speed chart and temporarily bring the target idle to 1800 and see what the IAC position % is... Your IAC Hold Position will need to be less than that % for your idle to return.

    Once you've got it working and understand the relationships you can fine tune for preference.

    Got it... will do! Thanks!

  16. #16
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    One last question before we give it a shot today... should I have to make any adjustments to the throttle body while trying to get the idle tuned in??

  17. #17
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    Check out these threads from the Holley EFI forum:

    http://forums.holley.com/showthread....e-Tuning-Notes

    http://forums.holley.com/showthread....ist-Holley-EFI

    This forum has been really helpful to me while tuning my HP EFI system. There is a guy on the forum named Danny Cabral that answers about 90% of the posts. He is a Holley EFI expert and is on the site very frequently.
    Last edited by andrewb70; 07-22-2013 at 05:29 AM. Reason: spelling
    Marc Battiste

    1969 Camaro
    LY6/T56/12 Bolt

  18. #18
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    Default Need to get educated on Holley HP EFI

    If your IAC is about 7% to 10% at idle then you should be set with the physical adjustments, the rest can be done in the computer. Make sure to do the TPS auto set if you do adjust the throttle.

    I agree with the previous post, Danny Cabral is very helpful on the Holley forum.

  19. #19
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    UPDATE:
    First off, thanks for the info! After exhausting all recomendations, the tune was ditched and another one was uploaded...instant gratification! All of the things you guys told me to adjust finally responded and the results were great. I will be taking the car on a longer drive this weekend and continue to get educated on the tuning so that it runs as well as it possibly can!! I am going to check the differences between the two tunes to see if I can identify the problem area. Regardless, idle/ramp decay/hold all work correctly now and I can drive the car!! Thanks again... and I am sure there will be more questions in the future!!
    Matt

  20. #20
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    Glad it's running. Keep us posted on your progress.
    No longer working at Holley



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