Need help I had a cylinder misfire on cylinder 4. I changed injector and plug. Fixed problem for about 3 weeks. Same problem again but cylinder 8. Did same injector and plug and only helped problem but car still runs rough but no codes show up. I am stummped. Please help. This is a 2000 Mustang GT 4.6

 

Did you try a coil?When a ford comes into the shop ,,with a miss...I isolate the miss to the particular cylinderand usually end up replacing the plug and coil on that cylinder...hardly ever an injector....

 

Could always switch out the coils to a near by cylinder and see if the miss follows the switch...