Yes, a catch can can hurt your engine if it is not installed properly or if it becomes clogged with debris. A catch can helps to reduce the amount of oil and contaminants from getting into the intake manifold, which would otherwise accumulate and cause problems such as decreased performance and damage to other parts in the engine. If the catch can is improperly installed, however, then this could lead to oil bypassing it altogether and entering directly into the intake manifold. This influx of oil could result in a decrease in fuel efficiency as well as potential damage to components like spark plugs or pistons due to incorrect air-fuel ratios being created by an excessive amount of oil passing through. Additionally, if the catch can becomes clogged with debris over time then there will be insufficient filtering taking place within its walls; this could also result in negative effects on engine performance or even more serious damage occurring over time.