2000 Nissan Xterra All Lights Pulsing

My Xterra ran great 6 months ago, slowly this problem has become constant. It starts rough sometimes, as if it is not firing all cylinders. When this happens I naturally give it the gas peddle as if it were carbureted and after a second it runs fine again. The real issue I am writing about here though is the constant flickering of all the lights and the engine speed. The tach only floats a hair but the lights alternate between normal and dim about two time a second at an idle and go faster as I accelerate. The check engine light came on and I went and had an autozone check it, they said it was either a knock sensor or a ground wire loose. I also had them check my alternator and battery, both checked out fine.
So
where should I start checking ground wires? And does that all add up to only one problem, or am I likely looking at multiple issues?