1999 Escort ZX2 code 301

I have a 99 Escort ZX2 with the 2.0L DOHC. Every so often the engine will run rough and the check engine light come on ad displays code 301 which is cylinder 1 misfire detected. I have changed the plugs (NGK plantium laser installed)and wires and still does it. I have tried high test fuel which seems to have helped but still does it every so often maybe every 400km for about 5 minutes then tuns fine again).

Any ideas on what else may be causing this would be appreciated.

Thanks in advance

I have a 99 Escort ZX2 with the 2.0L DOHC. Every so often the engine will run rough and the check engine light come on ad displays code 301 which is cylinder 1 misfire detected. I have changed the plugs (NGK plantium laser installed)and wires and still does it. I have tried high test fuel which seems to have helped but still does it every so often maybe every 400km for about 5 minutes then tuns fine again).

Any ideas on what else may be causing this would be appreciated.

Thanks in advance

Im not going to stand behind this obd older model computer codes. but it use to be: 301 missfire on cylinder 1