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Thread: Idle speed adjustment for TBI?

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    Idle speed adjustment for TBI?

    (89 S10 4.3 TBI "z")
    I need to bump-up my idle speed by about 50-100rpms, but the TBI has no adjustment screw. (I supposed the ECM regulates that) But has anyone fabricated their own? Or does any aftermarket company make a kit?

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    Double Bagged s10blaza's Avatar
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    http://s-series.org/Sections-article1-p1.html

    The idle screw is on the right side of the throttle body right under where "TBI" is stamped on it.

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    Do ya feel lucky? Teeleton's Avatar
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    Originally posted by s10blaza
    http://s-series.org/Sections-article1-p1.html

    The idle screw is on the right side of the throttle body right under where "TBI" is stamped on it.
    The computer is going to try to compensate for your changes though. Make sure that when you open the blades with the screw, that you adjust the TPS sensor so that it still reads the same. You might need to adjust it farther than you think, because as you open the blades, the computer is going to close the IAC to keep the idle in check. Eventually the IAC will be totally closed and then you can start to make a difference with the screw. Go slow so the computer can detect your change and react.

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    Your mom's box! slammins15's Avatar
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    From the factory the idle screws on a tbi are capped so you can't mess with them but here is how to set your idle speed on a tbi.First you need to access your idle speed screw on the front of the tbi you can see a little silver cap use something sharp and pointy I use a cheap o-ring pick and hit it with a hammer to pierce a hole in the cap.
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    Your mom's box! slammins15's Avatar
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    Then dig the cap out of the tbi using a 90* o-ring pick to expose the torx idle speed adjustment screw.Then follow the instructions on the s-series site for making adjustments.
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    Your mom's box! slammins15's Avatar
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    Originally posted by Teeleton
    The computer is going to try to compensate for your changes though. Make sure that when you open the blades with the screw, that you adjust the TPS sensor so that it still reads the same. You might need to adjust it farther than you think, because as you open the blades, the computer is going to close the IAC to keep the idle in check. Eventually the IAC will be totally closed and then you can start to make a difference with the screw. Go slow so the computer can detect your change and react.

    Teeleton
    Thats why you follow instructions and put the ecm in a closed loop so the IAC fully opens and you unplug it while making adjustments.
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    Originally posted by slammins15 [BThen follow the instructions on the s-series site for making adjustments.
    [/COLOR] [/B]
    Do you have a link to hese instructions?

    That torx screw looks like it's on the inside? What I did was wedge a small screwdriver between the throttle lever and is' stop on the body. It effectively raised the curb idle, and the computer didnt seem to attempt to slow it down?

    Can I bump the idle a small amount without the TPS & IAC coming into play? I want to avoid messing with that if possible. But if I have to, is that the only thing, the TPS?

    Do I unplug the TPS to neutralize it? Or, adjust it live? And how is it adjusted?
    Last edited by webslinger60; 08-09-2005 at 05:26 PM.

  8. #8
    Your mom's box! slammins15's Avatar
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    Originally posted by webslinger60
    Do you have a link to hese instructions?

    if you read the second post s10blaza already posted it thats why I made reference to the link and didn't post it myself. Read the instructions on how do adjust it properly it only takes like 10 minutes once you actually do it.
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    Question Another idle question.

    I've got a slow idle also 2001 4.3 . My question is, is there a reason (problem) that the ECM is slowing it down?

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    Double Bagged s10blaza's Avatar
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    holy crap this post is old

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    Quote Originally Posted by RED BOWTIE BLAZ View Post
    I've got a slow idle also 2001 4.3 . My question is, is there a reason (problem) that the ECM is slowing it down?
    Your 2001 4.3 is not a TBI engine, so its going to be a completely different setup.

    Usually the reason that the idle is screwed up is something going on within the engine, like a bad IAC or EGR or something of that nature.
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