My Haynes manual says when setting the idle, with the IACV unplugged, use a hand held tach to set the idle at 450 + or - 50 RPMs.

Now, the factory tach only goes down to 500 RPMs and I would doubt it's ability to be accurate that low.

What devices do you guys use when setting the idle?

 

if your running obd2 computer a hand held scanner should show within 50RPM.

 

a good automotive dvom will have an inductive pickup for this.
ie: Fluke 88

 

can I get some links to this stuff? thanks.

EDIT: are you talking about the scanners they loan from auto zone?