FYI to adjust the idle you need to disconnect the TPS and give the engine a few revs. Then use the screw to set the idle to 650. Once the idle has been set you can adjust the base ignition timing to 20 degrees BTDC using your timing light and rotating the distributor. Once you've adjusted the idle and/or timing, plug the TPS back in and you're good to go... Unhooking the TPS is important because it stops the ECU from changing the timing or using the IACV.
You said you don't have a tach and your engine is having troubles idling (presumably, stumbling/rough idle)? I think playing with the idle adjustment screw is the last thing you need to do right now (it's not going to solve your problems, it's more for fine adjustment of idle rpm due to altitude changes).
I suggest you do a quick tune up (plugs, wires, cap, rotor, fuel filter, clean MAF element, pull ECU codes, clean IACV) before you start changing things. If you post more symptoms of your problems maybe we can help you solve the real issues instead of just helping you making it worse
