To tighten a loose tire valve stem, use a valve stem core tool. Insert the tool into the valve stem and turn clockwise until snug. Avoid overtightening, which can damage the core. If the stem itself is loose at the base, it may require professional repair or replacement.
While there are some variations, most standard automotive tire valve stem cores are universal in size. This means the same valve stem core tool will typically work for the vast majority of passenger vehicles. However, some specialized applications, like those for large trucks or certain industrial equipment, might use different core sizes. Always check if unsure.