2.3L ('83-'97) What is the coolant line feeding the intake manifold for, cooling or heating??

[don4331]

The 3.0l Vulcan engines used heater hose lines to throttle body to prevent icing in that location
Icing will cause running issue in colder temps, under 45degF usually, fast air flow can get quite a bit cooler in the intake
Any moisture in the outside air can freeze on contact to colder metal
Ice particles are not great for air/fuel mix, lol, and icing can also cause throttle to stick

PCV Valves also use heaters as well, to keep oil vapor warmer so valve doesn't stick

Icing occurs when air flow through a narrowing of the intake - e.g. throttle blade or the venturi in a carb. So, when you're cruising 55 on interstate with throttle only a little bit open is an ideal situation.
It occur when air is above 32°F( below freezing the moisture in air is already frozen so can't refreeze in the engine), but close to the dew point (usually temperatures over 45°F are too warm for dew).
Icing would can cause venturi to ice over in carb, the throttle to stick or even ice the intake up so bad the engine stops (well, it was a Isuzu P'up).
Icing concerns is part of reason why light aircraft engines intakes run up through the hot oil pan in way to cylinders - nothing worse than engine stopping just before the trees.