Idling issue after car is warmed up
 

Ok I have noticed this issue more and more lately to the point where I feel like I need to solve it. BTW I have an '03 with 107k, engine is stock except for FIPK.

Sometimes when I come to a stop after I have been driving for a while, I notice what feels like a very slight misfire at idle. It is hard to describe but I will try anyways. I usually notice it when I have driven on the freeway and then get off and park in a parking lot and the car is just idling. At about 1 second intervals I hear what I would describe as a thud sound and I can feel it in the car. Before yesterday it was usually barely noticeable, and it doesn't happen all the time. Yesterday after I parked it was the loudest it had ever been and I could hear it outside the car from the exhaust.

I am guessing it is a misfire of some sorts but it is usually very subtle and not what I would normally feel a misfire is. I have spark plugs on order and they should be here in a few days. If anyone else has any ideas that would be great. I can try and describe the sound/feeling of whats happening better if that is necessary. If it happens again like it did yesterday I will try and get a video.

Thanks

edit: thought I should add that there are no CEL's