Fuel Mixture/idling speed

["Lino M. Valadas" <valadasl@osha.igs.net>]

Hi All,

I'm looking for help adjusting the fuel mixture and hopefully the idling
speed.
I have an 86 5ktqw.  
The plug on the mixture adjustment screw is no longer there, and the screw
goes out of adjustment by itself.  I can tell because the idling speed goes
up;  when I check the screw,  I can see it has moved (I had it marked).  So
I turn it clockwise (tightening it) and I bring the idling down.  I've been
playing this game for months, and I'm getting tired of it.
My questions are:

1. Is there a manual procedure to adjust the fuel/air mix?  Haynes manual
is totally useless here, it tells you to take the car to the dealer.

2. Does anybody know of a way to stop the screw from moving?  Do I have to
get a new plug from the dealer?  I  don't want to seal the screw until I
get the mixture right of course.

3. I've been thinking of buying an O2 gauge (bar graph).  Would this help
adjusting the mixture?  Do I have to wait for the gauge to make the
adjustment.

My fuel consumption has gone up substantially lately and I think its
related to my adjusting the screw blindly.

Any input would be appreciated.

TIA
Lino