Using a survey, interviews, and reflections by the teaching-research team, we explored the effects of almost a decade of experimentation, inspired by Freire's pedagogy for liberation, which applied participatory action research in engineering courses and in cities to develop professionals who are more committed to sustainability and more able to interact with 'ordinary' citizens in all their diversity. We found that using a planning-based participatory action research methodology, in the living laboratories of real city neighbourhoods, increased engineers' appreciation of citizenship, sustainability and equity. While this experience does not pretend to universality, it does suggest ways that structuring action research into course activities and critical reflection can improve students' understanding of sustainability and related social justice challenges. Moreover, this innovative pedagogy proved robust during two years of extreme disruption due to social protest and strict COVID-19 quarantines in Chile. The findings may benefit researchers and teachers grappling with similar challenges.