Took my car and had the check engine codes scanned. Came up with P0134 Heated o2 sensor bank 1 sensor 1 sensor circuit no activity detected. P0304 cylinder 4 misfire. And P1240 injector circuit open cylinder 4. I got some wires while I was there too and changed them out. Not sure if it helped yet though wont know til I try to start it tomorrow. How could changing the plugs really cause all those problems?