throttle body questions

[backporch]

I have two throttle bodies that I can choose from.

A lower mileage explorer that had a lot of corrosion and the springs look frail. My higher mileage Ranger engine that has one strange issue. The throttle is a little sticky when closed. There is a pin to limit the travel when closing and when the butterfly valve is closed, there is a gap. It seems like that limit "screw" should be adjustable, but doesn't appear to be a screw??

Is it possible to adjust this and can anyone suggest a lube or rust-proofing for the throttle coil springs?

 

[backporch]

On closer inspection, in much better light, that is an adjustment screw with a 5 or 5.5 mm head and very fine threads covered in rust. The gap between the throttle body and the linkage is the same on both but the position of the screws are very different.

I sprayed penetrant on the screw last night and will adjust that screw until it leaves the throttle body open a hair. I have also read that silicone spray is a good lube and will prevent corrosion, but can be dangerous by electronics, so must be controlled. WD40 is also an option. It seems to be more common to leave them dry, but I would like to hold off any more corrosion if possible.