420A misfire cylinder 4 need help

[masterjonny]

so i was driving home one day and all of a sudden my car sputtered and threw a engine code so i looked up the code and it said misfire in cylinder 4. what can cause this? i have brand new spark plugs and wires, and i tested the msd coilpack and its in working order. And I guess I have been running a little rich. Does anyone have suggestions on what i should do or buy? Thanks

 

[92AWDHX40]

Maybe wiring, the injector itself, how about the ecu pull it and inspect it for anything unusual.

 

[Gaines12]

It could be low compression in that cylinder which could be bad rings or leaky valves.