[Paul Ritland]

I have a 2005 Boxster S with some 48000 miles on it. In 2020 with 47000 miles I got a CEL indicating need to take it in for service. It was idling rough but seemed to be running well at speed. My OBD 2, indicated an intermittent misfire on one side. I took it for service and the coils and spark plugs were replaced. The apparent misfire at idle disappeared. In December 2022 the CEL indicated need for service and the OBD 2 gave me the same message, yet the idle was still smooth. The mechanic was unable to diagnose and cleared the reading telling me to return if the CEL returned. It returned in January 2023. My OBD again indicates an intermittent misfire on the same side. Before I return it to the mechanic, can anyone explain why this is happening?