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Thread: 98 F Body with LS3 Cold Start Issues

  1. #1
    Potential Tuner
    Join Date
    May 2020
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    Ontario, Canada
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    3

    98 F Body with LS3 Cold Start Issues

    Hello i am new to hp tuners i have been stuck chasing my tail the past few days. the car has been street and dyno tuned last summer and drives fine but i am having inconsistency with cold starting the car. only once in a blue moon would the car ever cold start without using the throttle pedal until it got some heat into it. went out to start the car today expecting it not to fire and it fired right up which i have log1 for it appeared to be calling for more idle airflow. let the car cool off for the rest of the day ECT was within 5* of the first start up and it was a no go.

    car is a 98 pontiac firebird LS1 car with a GMPP LS376/525 LS3 with a 92mm cable throttle body. cam specs are 226/236 @.525/.525 110lsa

    Any insight is appreciated

    cold start log 2.hpl
    cold start log 1.hpl
    Base Config.Channels.xml
    TA Start.hpt
    Last edited by Derek376; 05-19-2020 at 10:26 PM.

  2. #2
    Senior Tuner Frost's Avatar
    Join Date
    Jan 2006
    Location
    Richmond VA
    Posts
    1,950
    Just not enough airflow through that out of spec IAC passageway to get it to crank. The IAC is wide open there (ECM can't make it open any more) You can open the blade to offset it, but it will affect warm running. If the IAC counts are already low when it's a full temp, that maybe all you have.
    Steve Williams
    TunedbyFrost.com


  3. #3
    Advanced Tuner
    Join Date
    Feb 2015
    Location
    Perth, Australia
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    974
    drill a hole in the blade

  4. #4
    Quote Originally Posted by lukearmstrong1990 View Post
    drill a hole in the blade
    If the IACV duty is already low when the car is warm, he needs to address the low flow through the IAC opening. Increasing the airflow through the throttle opening either by increasing the opening when the throttle is closed or by drilling a hole will not be a good way to solve the issue because it could keep the ecu from being able to control idle when warm. I am going to guess its an Ebay 92mm TB, which if that is the case he will need to massage the IACV passage as I have seen them machined very poorly more than once. I have seen them so small due to poor machining that a 5.3 would idle at 1200 rpm with the IACV completely removed from the engine.