How do I readjust the idle? Is there a screw? If so, where is it? Some of the research I've done online says the 'screw' is 'tamper proof' and requires a special tool? Also I can't find photos showing where the screw is. I'm guessing you also have to hold the 'switch' down and the lid up to access the engine while running?
The idle screw is just a regular slotted screw, nothing special. I use a small screwdriver about 6" (150mm) long.
Just stand on the left side of the car, observe the throttle cable, and follow it towards the right side of the car. You should be able to see the quadrant (quarter of a "wheel"), and the screw is underneath. (OF COURSE)


It faces the left side of the car.
Turn the screw counterclockwise a bit (lefty-loosey), start with maybe a quarter turn with the engine warmed up but off. (less intimidating that way.) Then re-start the warm engine and see what the RPMs are.
Once you find the idle screw you can adjust it easily with the engine running.
I'd suggest aiming for 1000 - 1100 RPM at first. And BTW, that is with the lights on and the blower (heater only) on HIGH. (Large electrical demands lower the idle, so in order to prevent battery drain in traffic, this is how you prep for idle adjustment)
No need to hold the switch for the engine cover fan, when doing this.
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Again, your car has carbs, mine does not...but I think that the "tamper proof" refers to the idle mixture screws, not the idle RPM screw.
Maybe someone like
Esprit888 has a pic handy, I'm at work and I do not.