Hi all, I got my ‘05 sedan back in August and fell in love with it immediately. It runs fantastically, however, about three months or so after I purchased it I started getting these shudders at idle every couple of seconds, like a quick shake that lasts a fraction of a second then goes away. When it first started like this it came with a check engine light, shop said it was a misfire in cylinder 4 and that I needed new spark plugs. I opted to change the plugs myself rather than pay the shop an absurd amount to do it and rather just had them change my oil, which weirdly enough resulted in the check engine light going off and the shuddering issue to greatly improve. I still went ahead and changed the sparks which upon my own inspection seemed fine as they were and didn’t end up changing anything about the shuddering.

Over time the frequency of the shuddering has been getting worse and it seems to also get worse with oil life. Today I finally got around to cleaning the throttle body and mass air flow sensor hoping that this would help the problem and while it’s now running smoother than ever at speed it’s still shuddering bad at idle.

Anybody have any ideas about what might be causing this?