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Thread: Start-up Idle issues. This isn't a RAFIG/RAFPN issue

  1. #1
    Junior Member
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    Nov 2006
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    Default Start-up Idle issues. This isn't a RAFIG/RAFPN issue

    Hey guys, I'm having some problems with getting my truck to idle.

    First of all:

    It's a 1999 5.3L silverado with a tr224 on 112 lsa cam. I am running a 2002 operating system. I have my RAFIG and RAFPN nailed down to less than .2 for each. My truck is set to desired idle at 700 rpms and it holds it there perfect with less than a 50 +/- rpm change.

    Now my issue:

    On cold startup the RPM's will jump to about 1500 rpms and stay there until they slowly fall back down to desired idle.

    On warm startups the RPMS stumbles bad and takes a while to find idle. I have to give it gas so it won't die.

    It seems as if the problem is opposite with each other on cold and warm rpms start-ups.

    I have searched and searched and searched with no luck.

    Here are a few more things to point out. I have been told that it may be a cranking VE table issue. I don't have a wideband(yet). Is there anyway around that issue to get my truck to idle better?

    Something else to note: I upped my high octane spark table 5% and it seemed to have made the problem worse on warm startup. It may just be a coincidence, but I'm trying to give out as much info to you guys as possible so that you can hopefully give me some input.

    Like I said, everything else is great, I'm more than happy with my tune but it's this startup idle issue that's killing me.

  2. #2
    Lifetime Member TAQuickness's Avatar
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    Jan 2005
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    Take a look at the start up airflow values (startup airflow and startup friction). Those could help you get a handle on the start up airflow. You can also look at afterstart enrichments along with the cranking VE


  3. #3
    Lifetime Member Doc's Avatar
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    What are your IAC counts when this happens? What are they when fully warmed up?

    2000 Silverado Full Size 4x4: Forged 6.2, H/C F1R Procharger
    98A4 Z28: 02 PCM H/C Forged 347, 9" Moser 3.73
    V1 V2 99+up RR COS #5 OLSD Dual Stg N20
    www.efialchemy.com
    www.greatamericancarwar.com

  4. #4
    Lifetime Member Rhino79's Avatar
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    Add a couple hundred rpms in the Startup> Startup RPM offset table and also subtract about 50% from the Startup Friction Airflow Decay in the corresponding temp ranges, that should fix that problem. I had a 224 cammed 6.0l do the same thing to me before.

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