2002 WRX Wagon, stock everything, 94,000 miles, all engine & drive train parts are original.
For the past year or two, when at a full stop, I can feel the car vibrate while the engine is idling. It happens more when the engine is still cold (not surprising), and it happens more when it's humid out. But even after the engine warms up (reaches about 190°F according to my ODB II readout), it still does this a little bit. Enginre RPMs are fairly stable - about 720 RPM warm, a little over 800 while the engine is still warming up.
Everything else about the car is fine. There's no hesitation when driving, and I feel like I had as much power as the day I bought the car. But I don't remember experiencing these vibrations when the car was younger -- even when the engine was still cold.
1. Is it anything to be concerned about?
2. Anyone have any guesses as to likely cause?