I am having an issue with a check engine light that keeps popping up. When it first appeared the fault code was for misfire in cylinder 4. I took the opportunity to change all the spark plugs with factory NGK and all ignition coils with VW coils. I had the engine fault codes erased. It has been two weeks and engine was running great, but in the last few days it has been idling rough and the check engine light came on again. The rough idling happens at about 1100 rpm and u can feel vibrations in the car. I had the code checked again and it said misfire in cylinder 4. Anyone have thoughts on what this could potentially be??