Any one know the right way to adjust the Idle screw?

The Fiero does not have an idle screw, at least that is not what it is for.
The screw is actually just a stop to keep the butterfly from going all the way shut and sticking.
The idle is controlled and set by the IAC motor and the ecm.

If your screw has been moved and you are trying to set it back where it should be there are a coupld methods that others have used.
One is to back the screw out until the butterfly startes to close all the way and you can feel it sticking when you go to open it and then bring the screw back in a 1/4 -1/2 turn.

The way I like to do it is with Winaldl. I've only done it on V6's
If you are sure you don't have any vac leaks. (engine should die when you cover the iac port) I get the engine warm and while watching the IAC count with winaldl I set the screw for a IAC count of 30-40 and seems to work well.

My 2 cents on it anyway... nickel for inflation.

Normally the idle screw doesn't need to be adjusted. It's set at the factory and covered by a brass insert so that it can not be tampered with.

I had to adjust mine after a rebuilt my engine. I had the throttle body bored out. When I got it back, the brass cover was missing. I has an erratic idle that I couldn't find the solution to. After a search, I found this thread.

https://www.fiero.nl/forum/Forum2/HTML/080905.html

The sixth post describes a method to set the idle screw. I followed that procedure and haven't had any problems with the idling since.

If the brass idle screw cover is still on your car, then the idle screw setting is probably not the issue. You probably have a bad sensor or iac valve.

Skybax wrote this a while back.

quote If everything is working properly, no exhaust leaks, no EGR leaks, and the engine is properly tuned, you can go through the IAC system. Idle is controled by the IAC valve (idle air control) via the computer and is not adjustable. You can go over the system if your not happy with where it is idleing. Proper idle for the V6 is roughly 900 RPM. The set screw in the throttle body is for minimum air flow through the throttle plate which is often misunderstood as the idle screw. Any tweaking of the throttle stop screw will give the ECM fits. The ECM wants to be in control of the idle and is not happy when it can't control it. If the normal learn limits of the ECM are exceeded, they will be reset to nominal, causing an erratic idle. The IAC and associated passages need to be clean to work right. Remove the IAC carefully. You can clean it (the nipple) using carb cleaner and a small brass brush or rag. At this time also clean the throttle palte. Once clean, install the IAC back in the throttle body and reconnect the IAC wires. For the ECM to properly control idle, the throttle stop screw must be set for "minimum air". This is a process that sets the idle with the IAC fully extended. To fully extend the IAC, jumper ALDL pins A and B together (just like when you check codes) and turn the key on, but do not start the car. With the key on, not running, and in diags mode, the ECM will keep trying to fully extend the IAC. After 30 seconds or so, pull the IAC connector off the IAC *before* doing anything else. This will capture the IAC fully extended. Now pull out the jumper in the ALDL, and start the car. Typically the "minimum air" idle speed is in the 500 RPM range. I find the car can bearly run at 550. So as long as you can get it to idle on its own between 600 & 700 your good. Set the idle using the throttle stop screw. (The engine should be fully warm to do this.) Now shut the engine off and reconnect the IAC wires. The ECM does not know where the IAC present position is, so pull the ECM fuse (or disconnect the battery) for 20-30 seconds. (This will cause a complete ECM reset of all learned parameters, including the learned IAC ones. Then reinstall the ECM fuse. Turn the key on, wait 10 seconds or so, and turn the key back off. This will now reset the IAC to a known key-off "park" position. Now start the car. The engine should idle properly under control of the ECM. There are some learned values, such as an IAC offset for A/C, etc that need to be learned, but this will happen under normal driving conditions. I suggest driving the car right away under all conditions. Stop & go, steady cruising over 45 mph, full throttle, and so on. Pull over a few times and turn the car off, then restart it. The IAC can only learn X amount of counts with each run position. If everything else on the engine is in good condition and operating properly it should be around 900 RPM after coming to a complete stop with slight variations and improve over time. Mine is almost rock solid at 925 RPM.

I will say this, it's much more precise if you have an auto scanner to work with. I borrowed one from work, used it to actually "see" what my TPS was at as I adjusted both my V-6 and my Duke engines.

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jetman
Silver 86 SE 2M6 4-speed, with "check wallet light"
Now fortified with 8 essential slices of bacon goodness