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Thread: 1st Fuel Injection/ Affordable FI 350 TPI, AIC is acting weird

  1. #1
    Electronic Ignition!
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    1st Fuel Injection/ Affordable FI 350 TPI, AIC is acting weird

    I replaced my coolant temperature sensor and my hard starting has got a bit better. As soon as I did this my AIC was acting weird. A noticeable "vacuum sound" it never had before on start up and for quite a while. When it was noisy vacuum moved from 15-19 lbs, idle fluctuated too.

    i thought it was to the place where I could live with it and on a hot restart the AIC went crazy and started hunting , up/down, vacuum was all over the place. Do AIC screw up like this or is it something else?

    I really am starting to hate on this motor.

  2. #2
    Fuel Injected!
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    Someone smarter than me will reply to this, but try disconnecting the battery, performing a capacitive discharge (connect the positive and negative cables together ONCE THEY'RE OFF THE BATTERY), let it sit for a few minutes and then reconnect them, perform your IAC basic setting and then start the engine.

  3. #3
    Electronic Ignition!
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    Quote Originally Posted by sgtpoliteness View Post
    Someone smarter than me will reply to this, but try disconnecting the battery, performing a capacitive discharge (connect the positive and negative cables together ONCE THEY'RE OFF THE BATTERY), let it sit for a few minutes and then reconnect them, perform your IAC basic setting and then start the engine.
    thanks, I am trying to learn this stuff.

  4. #4
    Super Moderator Six_Shooter's Avatar
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    Quote Originally Posted by sgtpoliteness View Post
    Someone smarter than me will reply to this, but try disconnecting the battery, performing a capacitive discharge (connect the positive and negative cables together ONCE THEY'RE OFF THE BATTERY), let it sit for a few minutes and then reconnect them, perform your IAC basic setting and then start the engine.
    Don't do that, connecting the cables together, that is. In some newer vehicles, this can be seen by the air bag system as an accident in progress and set off the air bags.

    In other vehicles, especially ones with large audio systems that have large stiffening capacitors, this can damage them. In other devices the quick discharge can damage the circuit boards or the devices themselves.

    Also there's ZERO reason to connect the cables together. Other than vehicles that do have the aforementioned large audio systems with stiffening capacitors, the time it takes to power down the modules is less time than it takes to touch the cables together. If the vehicle does have a stiffening capacitor installed, it's easy to remove it from the affected systems, by simply removing the under hood fuse for the system.
    The man who says something is impossible, is usually interrupted by the man doing it.

  5. #5
    EFI GearHead ! EagleMark's Avatar
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    Now that the ECM is reading the right temp the IAC is probably working correctly so you hear the vacuum noise from IAC letting in or limiting air.

    Vacuum fluctuation is from the idle hunting.

    What's done to the motor? Has it been tuned for the changes?

    1990 Chevy Suburban 5.7L Auto ECM 1227747 $42!
    1998 Chevy Silverado 5.7L Vortec 0411 Swap to RoadRunner!
    -= =-

  6. #6
    Electronic Ignition!
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    Quote Originally Posted by EagleMark View Post
    Now that the ECM is reading the right temp the IAC is probably working correctly so you hear the vacuum noise from IAC letting in or limiting air.

    Vacuum fluctuation is from the idle hunting.

    What's done to the motor? Has it been tuned for the changes?
    It has Edelbrock heads, 1st FI Manifold, Affordable FI harness, headers, small cam. Tune was done from supplied info by Scott Hansen from Reno, NA.
    I am just about ready for some data logging, new to this so I am hoping to resolve any issues soon.

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