Are there prepositions that cannot be replaced by "je"?

Question

I have often heard that you can use je when doubting which preposition to use. Is this always the case?

Answer 1

Je is not intended for occasions of doubt, but rather when a preposition is needed but none of the defined prepositions are suitable. In practice, je is used infrequently, and most often in set phrases.

• Time espressions (je la tria horo)
• je via sano
• je la barbo de Zamenhof!
• plena je io (although plena de io is more common.)
• graveda je knabo
• mi kredas je Dio