Explain the IAC system to me
03-22-2003, 09:25 PM
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Explain the IAC system to me
Can someone explain the IAC system to me? I know how it works and what it does but I'm just more curios as to why a controlled vacuum leak smooths out idle. What would happen if it closed up? What would happen if it got stuck open? Assume its on a stock TPI car.
03-22-2003, 10:08 PM
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Car: '87 Camaro LT
Engine: 355 L98
Transmission: T56
if you apply no pressure on the throttle, the throttle body plates are closed and don't allow much air into the engine so the IAC motor opens up to feed air. it opens more when the engine is cold to bump up idle
03-23-2003, 12:10 AM
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Car: 82 Z-28
Engine: 383 TPI
Transmission: 700R4
The throttle plates have an adjustable stop, like a idle speed adj on a carb'ed eng. This adjustment is called the "minimun idle screw". It is set so eng barely runs while in gear (~450-500 rpm).
The IAC is completely closed for this adjustment.
The IAC opens slightly, allowing more air to enter eng bringing the idle speed up to normal levels.
The IAC also opens a little further when eng is cold and when additional loads are applied to eng while at idle. The A/C compressor being a good example of additional load.
If IAC sticks wide open, idle RPMS could be over 2500 RPMs in Park or Neutral.
The IAC is completely closed for this adjustment.
The IAC opens slightly, allowing more air to enter eng bringing the idle speed up to normal levels.
The IAC also opens a little further when eng is cold and when additional loads are applied to eng while at idle. The A/C compressor being a good example of additional load.
If IAC sticks wide open, idle RPMS could be over 2500 RPMs in Park or Neutral.
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