I've had this 09 impala for a little over a year and the whole time I've had it I've had this problem. When my car is idling it has a small rpm jump and shakes. It's not a constant shake. But it will shake a second then stop. Then shake. Then stop. It never goes away in idle. The car runs strong. I've never had any issues with the perfromance. I took it back to the dealer a couple weeks after buying it and they claimed they didn't see a problem. But my car should not be running like this. Its not causing issues but it's rather annoying and makes me feel as if the engine is not healthy. Any input would be appreiciated! Thank you.