[bowlofturtle]

I was talking to a toyota salesmen about a tune-up the only thing that he listed that i couldn't do is idle timming and idle speed adjustments. At school my teacher had a light gun but i never got to see how it was done. but can we adjust idle speed and timing on our own.

 

[Hajoca]

In short, the idle speed is adjusted to prevent stalling/starvation in an engine fuel system.

In most cases a higher idle speed is automatically adjusted by the ECM and some sort of servo motor (electric, or vacuum)

The set point (screw) is on the throttle cam, where the cable is attached to the throttle arm. Usually it is painted or glued to prevent it from being changed or adjusted.