with the engine running. You should notice a difference in how the engine runs. If no change then troubleshoot why your not getting ignition at that cylinder. It's usually something other than the coil packs because they hardly ever go bad. The most likely cause is bad connections to the CAS, PTU or injector connectors. Or a bad CAS or PTU. If you have ever disconnected the ECU make sure the connector going to it is well seated too.