Injector failure is most commonly caused by the breakdown of the polymer covering the coils in the actual injector. This causes the miniture-magnetic-field-inducing coils to short out therefore making them less effective at releasing the spring loaded body that opens to let the fuel spray through. (when energized magnetic field forces injector open) Therefore, running injector cleaner through the system may help but usually does not greatly decrease the problem. Only sure cure is new injectors.