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How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

This is a discussion on How do I adjust Idle on my OBS Tbi 350 1995 Tahoe? within the Performance forums, part of the General Discussion category; Any info is appreciated. thanx also, is there a screw on the tb?...

  1. #1
    Registered User 87vertgt's Avatar
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    How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?


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    Any info is appreciated. thanx

    also, is there a screw on the tb?
    1995 2 Door Tahoe-Lade 5.7 350 TBI, K/N Intake, CFM bored TB, Helix spacer, Hooker full length header, Magnaflow muffler, Magnaflow high flow cat, Ebay chip (didnt do s h i t) Msd coil, Msd Wires, Pullys, Big 3 Upgrade, 250 amp alternator....looking for more bolt on's

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    Registered User todd1969's Avatar
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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    Standing in front of the engine facing yor TBI. Remove air cleaner assembly and filter and anything else atop TBI. On the lower right area of the TBI you'll see a round slightly raised dimple area. About the size of a pencil. That's a plug covering your idle adjustment screw. It's not completely flat, kinda protrudes outward a bit. You'll either have to drill it out or CAREFULLY tap it with a hammer and punch. Go easy and tap carefully because that TBI body is not super strong. Crank-break that and its new TBI time quite possibly!

    Once you get the plug out, use an Allen wrench to adjust it. Real easy to adjust once you get the plug removed.

    I'll try and get you a picture of mine if my digital camera battery isn't dead.
    TBIChips Custom chip, 180 stat, 1" spacer,Witch Hunter injectors, Performance module-Cap-Rotor and 50,000 volt "Screamin' Demon" coil, Taylor 8.2mm wires, AC Delco plugs, true-duals, Magnaflow hi-flow cat, Spin-techs, 2" drop shackles...more after that!

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    Registered User 87vertgt's Avatar
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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    Quote Originally Posted by todd1969
    Standing in front of the engine facing yor TBI. Remove air cleaner assembly and filter and anything else atop TBI. On the lower right area of the TBI you'll see a round slightly raised dimple area. About the size of a pencil. That's a plug covering your idle adjustment screw. It's not completely flat, kinda protrudes outward a bit. You'll either have to drill it out or CAREFULLY tap it with a hammer and punch. Go easy and tap carefully because that TBI body is not super strong. Crank-break that and its new TBI time quite possibly!

    Once you get the plug out, use an Allen wrench to adjust it. Real easy to adjust once you get the plug removed.

    I'll try and get you a picture of mine if my digital camera battery isn't dead.

    COOL, THANX BUD

    DO I HAVE TO REINSTALL THAT PLUG?
    1995 2 Door Tahoe-Lade 5.7 350 TBI, K/N Intake, CFM bored TB, Helix spacer, Hooker full length header, Magnaflow muffler, Magnaflow high flow cat, Ebay chip (didnt do s h i t) Msd coil, Msd Wires, Pullys, Big 3 Upgrade, 250 amp alternator....looking for more bolt on's

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    Registered User todd1969's Avatar
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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    I pitched mine and never looked back.
    TBIChips Custom chip, 180 stat, 1" spacer,Witch Hunter injectors, Performance module-Cap-Rotor and 50,000 volt "Screamin' Demon" coil, Taylor 8.2mm wires, AC Delco plugs, true-duals, Magnaflow hi-flow cat, Spin-techs, 2" drop shackles...more after that!

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    vato cxpcman's Avatar
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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    i could be wrong but isn't the idle adjusted automatically?? .. if its over reving or under reving at idle something is wrong because the iac isn't working as it should be .. but what do i know about engines .. i remember reading from airdeano a procedure to do it .
    Cheyenne '81 sidestep, yellow, 5.7L
    Silverado '88 sidestep, gold, 5.7L
    Cheyenne '90 sidestep, brown, 4.3L

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    Registered User todd1969's Avatar
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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    I do believe the TBI is supposed to be idle adjustable. Airdeaon would know for sure, as well as Pauly I bet. I've adjusted mine after mods I tried, especially after installing underdrive pulleys, when I had a electric fans for a while, and just to get a more comfortable feel while sitting at red lights.
    TBIChips Custom chip, 180 stat, 1" spacer,Witch Hunter injectors, Performance module-Cap-Rotor and 50,000 volt "Screamin' Demon" coil, Taylor 8.2mm wires, AC Delco plugs, true-duals, Magnaflow hi-flow cat, Spin-techs, 2" drop shackles...more after that!

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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    That screw is called the "MINIMUM AIR ADJUSTMENT", basically it keeps the IAC from having to over-correct. Too much IAC opening is a bad thing. Here is the procedure to set it. Knock/Drill the plug out, get a TORX screw driver (not allen), and use this procedure or you might get undesired operation.

    A.)Fully warm up the engine
    B.)A/C off, electrical loads off, transmission in park/neutral
    C.)Shut-off engine and jumper A-B (top right and 2nd from the right)on the diagnostic terminal.
    D.)Turn Key to on, but don't start the engine (you should hear the IAC close)
    E.)Disconnect the IAC electrical connection and remove the air cleaner (It is important to do this with the Key On and the diagnostic terminal jumped as it fully seats the IAC)
    F.)Open the screw about 3-4 turns
    G.)Start the engine
    H.)The idle will be too high now, slowly close the screw down for the desired idle speed. It is important to note that trying to go up in idle speed is a waste of time, the ECM takes the TPS voltage reading at start-up and uses it for 0% TPS. If you start opening the throttle for a higher idle it increase the TPS reading above 1% and takes the ECM out of idle mode. Once out of idle mode, the adjustment is now off.

  8. #8
    Registered User 87vertgt's Avatar
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    Re: How do I adjust Idle on my OBS Tbi 350 1995 Tahoe?

    I adjusted it...very easy. there a threaded plastic bolt? that you can twist with your fingers...I moved it just slightly and now the alterntor charges at reds lights
    1995 2 Door Tahoe-Lade 5.7 350 TBI, K/N Intake, CFM bored TB, Helix spacer, Hooker full length header, Magnaflow muffler, Magnaflow high flow cat, Ebay chip (didnt do s h i t) Msd coil, Msd Wires, Pullys, Big 3 Upgrade, 250 amp alternator....looking for more bolt on's

 

 

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