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Thread: Idle AFR and Idle surge

  1. #1
    Lifetime Member Biggsy's Avatar
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    Jan 2007
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    Default Idle AFR and Idle surge

    Ok, I'm at a dumb mental blank.

    If I want to change AFR@Idle, there is no specific table for idle right?
    Use the AFR open loop table cells {B3605} that relate to idle right?

    Also, just got a new (S/H) car and am in the middle of tuning it for SD, got the VE table all sorted and fueling is smack on. I have a problem with idle where if I stab the throttle (not in gear) the revs appear to over correct and swing backwards and forwards 100-150 rpm either side of the commanded idle rpm. It will continue to do this until I either go for a drive or hold the revs up around 1500-2000rpm for a few seconds and slowley release the throttle.
    Any ideas on what this could be? I have made sure the timing has smooth transition between tables and even tried zeroing the under/over speed correction to stablise timing (because I wanted to eliminate timing as an issue, but I have put it back how it was)

    I don't understand throttle cracker and follower settings, but I am guessing it has something to do with these.

    If I put the Maf back in, this problem dissapears.

    TIA
    Dave.

  2. #2
    Lifetime Member SSpdDmon's Avatar
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    Jun 2005
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    Default

    Sounds like your fueling in the top cells of the VE are off....possibly rich. When the revs drop down to that region, the car is probably flooding and hurting the other corrections that are trying to be made via the IAC and timing. Tuning that part of the VE is a guessing game...

    To try and help prevent from falling in that region, you could always play with the throttle follower....like maybe slow down the decay rates that apply when you're sitting at idle. Check my idle thread in the tutorials. There's a lot of useful info in there.

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