Could be a dodgy injector or more likely as said a errant EARTH signal.
The injectors are LIVE all the time(when ignition ON), the earth is switched by the cu so if a bare(earth)injector wire is resting on earth somewhere, and moving around it will fuel constantly, or if indeed it jams open.
Might be worth having them cleaned in case of obstruction in pintle of no 3.
tabetha