Idle issues!!!!!!!
 

I have been trying to solve this issue forever and it's driving me nuts.

My 85 GSL-SE 6 port when at operating temp the idle drops like a rock after driving and then coming to a stop. It slowly creeps back to about 800-850. There is no AC or air pump on the car.

The TPS is set perfectly.checked it today. Now from what I can read I think it's the throttle stop screw....now this screw is the smallest most fragile little screw I have seen. Can somebody tell me how to adjust this.

As a side piece of info. If I unplug and block off the BAV valve the car fires up then stalls instantly. Any help aaaaaaanybofy can give me would be amazing!

Cheers!

Lot of miles on car? Manual trans? If you keep your foot on gas and feather throttle will it keep running @800 rpm? Has throttle
body ever been cleaned? Normal for throttle body,dynamic chamber to get gunked up,dirty. They need to be cleaned periodically.
Disconnect the boot from throttle body that comes from air flow meter and look inside throttle body(with flashlight),operate linkage and look for a ring of dirt in primary throttle plate bore where throttle plate is in closed position. Look also at the blade itself. If these have
never been cleaned,most certain there will be buildup of dirt on them. BEFORE you do any adjustments,using throttle body cleaner(CRC makes a good product-try to avoid use of carburetor cleaner spray) and thoroughly spray and clean the area around throttle plates,and plates themselves using an old toothbrush and finally a shop rag with throttle body cleaner sprayed on it for a final wipedown. Follow up with a light application of light oil(CRC powerlube excellent for this) on throttle shafts and make certain all works smoothly. Reinstall air boot.
Remove BAC valve from intake manifold and separate valve from control motor again using throttle body cleaner,clean(valve portion-not motor) thoroughly and blow out with air. Lube valve assembly with powerlube and reassemble. With care the gaskets for each won't tear on disassembly,if they do,you can make replacements out of thick gasket paper sourced from any auto parts store.
Before installing BAC valve assembly,hook up jumper wires to plug and to battery and test operation. Should hear valve moving with voltage applied and move back with it removed. Reinstall. Start and warm up car,idle speed should be very close to 800-850 rpm. If close,use idle air bypass screw on top of throttle body housing to make small adjustments. This is good for compensation of @150 rpm
either way,clockwise lowers,ccw raises idle speed. The"fragile"screw should only be adjusted if bypass air screw doesn't give enough range of adjustment(not likely). Any adjustment of this screw will change calibration of tps and it will need to be readjusted also. Pic of idle air bypass screw..