Idle adjustment

Tiny
HASSAN SHUAIBU
  • MEMBER
  • 1995 HONDA ACCORD
  • 2.7L
  • V6
  • 220,123 MILES
What is the difference between idle adjustment using the screw on the IAC valve and throttle cable adjustment that have pair of nut one for adjustment and the other for tightening? The throttle cable pass through the nuts and goes into cruise control device unit. The nuts can be adjusted to increase or decrease idle speed.
Wednesday, April 26th, 2017 AT 3:35 AM

1 Reply

Tiny
CARADIODOC
  • MECHANIC
  • 33,869 POSTS
Those nuts are not used to set the idle speed. They are used to remove the excessive slack in the cable so the cruise control will respond accurately and hold the right speed. If you try to use them to control idle speed, it can surge when the engine rocks and tugs on the cable. There must be a little slack in the cables.

There is no idle speed adjustment on computer-controlled engines. The idle speed motor is pulsed to various positions by the Engine Computer to set the desired idle speed. As the motor slowly rotates, it turns a threaded rod with a valve on the end. That valve exposes more or less of an air bypass passage around the throttle blade. At the same time, the computer adjusts the amount of fuel spraying into the engine.

On those few engines that still have an idle speed screw, that simply sets the starting point, then the computer continues to make the changes it wants by running the idle speed motor. If the idle speed screw is used to increase idle speed, the computer will just close the idle speed motor and valve to bring the speed back down.
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Wednesday, April 26th, 2017 AT 2:12 PM

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