Infrequent but recurring P0303 cylinder #3 misfire. Replaced coil and solved for a couple weeks. Replaced plug with same result. Swapped #1 and #3 coils and just threw code again. Have no noticeable performance issues with acceleration or gas consumption. Not throwing code only when engine warms as it's been warmed numerous times before code reappears.

 

How many miles on the car? Have you ever had the intake valves cleaned/walnut blasted?

 

Thats what I was going to ask also, did you have a carbon blasting like this or at the dealership?


https://www.northamericanmotoring.co...-cleaning.html