I have been fighting to get rid of a misfire on #3 for a while now. All new ignition parts and injectors. I have the valve cover off and doesn’t seem that the lifter is collapsed. Only other thing I could think of is an issue in the injector wiring. The misfire seem worse at idle than driving. Anyone have any suggestions?
2016 suburban LS4 5.3

 

you will need to take it to a shop and have it properly diagnose, trust me it’s less expensive than running the parts cannon. You need to verify the injector pulse command, ignition coil secondary and primary, make sure the intake and exhaust valve are actually opening on that cylinder, run a compression test on that cyl as well. At the very least you need an oscilloscope and a compression tester which is easily 5000$ plus to properly diagnose this… if you want to at least make sure the valves are opening and closing on that cylinder have someone crank for a second or two with the rocker arm cover off.