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Thread: Throttle Issue

  1. #1
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    Default Throttle Issue

    I have an LT1 motor controlled by 411 PCM. When I blip the throttle there is almost nothing there(RPMs go down) which makes for tough time driving a stick car. On the other end of the spectrum, when I get into the throttle fairly hard and let out the RPMs hang up BAADDD....motor will literally stay revved at 4500RPM or 5k until I shift and get it into the next gear. I have had to shut the car down with it hanging at 6k RPMs before when getting into it hard and then throwing the car in neutral.
    I believe it is throttle cracker and follower I need to mess with, but It appears as they are already maxed out in the software? Should I go back the other way? I haven't really messed with it and don't have a full understanding of how it works. current_01.ctz

    I attached my tune file. Also, the car is Procharged 396ci, monoblade throttle body, Manual Trans

  2. #2
    Joe (Moderator) joecar's Avatar
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    You have cable-throttle (not DBW throttle), right...?

    Yes, try going the other way.

    It could mean that your VE and/or MAF tables are under-reporting.

    I see that many tables have been changed... set as many tables as you can back to stock (especially the idle tables)... but do account for IAC effective area since your throttle body is different.

    Check for air leaks (including due to EGR mechanism being broken and letting air leak in).

  3. #3
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    The car is cable throttle, correct. It has the 93-97 style LT1 engine with an aftermarket LARGE monoblade throttle body. The VE table seems to operate well and the car drives nicely except for the two conditions listed. (throttle blip/bog and hard acceleration, then getting out of it RPMs hang up). The car is running a custom operating system and is speed density due to the procharger forced induction.
    There doesn't really appear to be any vacuum leaks, the cam doesn't produce a lot of vacuum in general. No EGR, no air pump, no emissions, etc...
    I just need to know how to go about making adjustments to the cracker and follower. Which tables should i start with and how should I go about modifying them.
    Also my IAC counts begin to rise as soon as I start driving the car, I will include a data log as to show how the counts rise from around 55 to 80 to 120 rather quickly.
    I may be able to get my hands on a roadrunner which would make this whole process much, much easier.
    Last edited by chevyunderpressure; August 21st, 2018 at 08:41 AM.

  4. #4
    Joe (Moderator) joecar's Avatar
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    +1 Roadrunner will make this easier.

    Read thru these:
    RAFIG-PDF-Includes-all-of-SSpdmon-idle-info
    Idle-Tuning-Helpful-Info-Inside
    Auto-VE-questions post#4

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