Yes ... the hanging idle can arise out of nowhere 
but
There really are some reasons it can happen
The pcm will keep the idle a bit high and it is based upon speed that the
VSS sensor outputs to the pcm.
First and Formost ... Learn from the dizzy thing you just did :Word:
Get data B E F O R E making a change
cause
This give you a baseline or reference point
First thing I would do is ......
1) count the amount of turns it takes you to gently seat the tb bleed screw
2) put it back to its original setting
3) report back to us that amount
Grady
but
There really are some reasons it can happen

The pcm will keep the idle a bit high and it is based upon speed that the
VSS sensor outputs to the pcm.
First and Formost ... Learn from the dizzy thing you just did :Word:
Get data B E F O R E making a change
cause
This give you a baseline or reference point
First thing I would do is ......
1) count the amount of turns it takes you to gently seat the tb bleed screw
2) put it back to its original setting
3) report back to us that amount
Grady
AND I have a wideband that I can use driving down the road. If I move the timing, I can see the Air/Fuel Ratio changes. Which is a great thing to have when I get to hit that bottle again.