Many engineering classes are highly sequential, causing students that fail to grasp initial topics to struggle as courses progress. Despite instructor exhortations to master fundamental subjects, students often continue to struggle instead of investing the time to review. Because students do not proactively re-learn initial content, a competency-based approach was implemented in a highly sequential thermodynamics course. In the approach, students scoring below 80% on the first exam were required to pass an online review quiz in order to take subsequent exams. Only 3 out of 135 students were unable to take the second exam, but all were able to pass by the time of the third exam. Significant increases (p<0.01) were achieved in both the average course grade and average grade on the third (final) exam as compared to the previous offering of the course, with the average grade on the final exam rising from 66.5% to 74.0% and the overall course grade rising from 76.2% to 83.2%. The competency-based structure forced students to review fundamental material that is necessary both later within a course and in subsequent courses, and seems to particularly benefit the poorer performing students. This may have impacts on student retention and persistence.