The case study described in this paper investigates the relationship among some pre-instructional knowledge, the learning gain and the final physics performance of computing engineering students in the introductory physics course. The results of the entrance engineering test (EET) have been used as a measurement of reading comprehension, logic and mathematics skills and basic physics knowledge of a sample of 47 Computing Engineering freshmen at the University of Palermo (Italy). These data give a significant picture of the initial knowledge status of a student choosing engineering studies. The students' physics learning gain has been calculated using a standardized tool in mechanics: the force concept inventory (FCI). The analysis shows that mathematical and physical background contribute to achieve a good final preparation in physics courses of engineering faculties; however the students' learning gain in physics is independent of students' initial level of mathematics skills and physics knowledge. Initial logic skills and reading comprehension abilities are not significant factors for the learning physics gain and the performance on physics courses. (Contains 6 tables.)