Pendejo is a vulgar Spanish-language term of abuse. To call a person a pendejo is essentially to call him stupid, although it also carries implications of wilful stubbornness and rank ineptitude.
A toilet may run periodically due to a problem with the flapper, the flapper seal, the flapper chain or a high float.
A worn flapper may cause your toilet to come on by itself. A toilet that comes on by itself wastes water and results in higher utility bills. A simple leakage test can confirm that in most cases the culprit is the flapper that sits over the drain at the bottom of the tank.