I have seen remedial courses before a first undergraduate calculus course that consist of a mix of algebra, trigonometry and coordinate geometry. However, have there been any experiments with remedial courses focusing more on developing problem-solving skills and/or the basics of what one would usually see in a transition-to-higher-mathematics course? If so, were such experiments successful in improving performance in calculus?
Note that while this is a general question, my specific interest at the moment is in assisting engineering students just beginning their undergraduate studies. Some of them only just scraped through in secondary school mathematics, while others have first completed a technician-style course that is light on mathematics.