Okay, so I have a 2008 Honda Civic LX Coupe(Automatic), I bought it in May, used with 36000 on it and now it has 47500. The problem occurred after I drove from Mississippi to Boston. What exactly is happening is after driving and the car is sufficiently warmed up, when I come to a stop light or park my vehicle, you can feel it shaking, the RPM's drop to about 600-650 and once in a while they completely drop below 500 for a split second and it feels like it is going to stall. When sitting in the passenger seat you cant feel any of the vibrations really, only in the driver seat are they noticeable and if you pop the hood you can notice the Engine vibrating pretty heavily. If I put the AC/Heat on low settings the vibration is masked usually, which I find weird. I've had up to date oil changes and have recently changed the tranny fluid(before I left Mississippi) I've checked the Air filter and it is clean. A hypothesis I have is possibly the engine mounts, but I do not know how to check them to see if they need to be replaced or tightened. I also took it to a Honda dealership and they ran a diagnostics test and all they came up with was a software update which didnt work and when I brought it back they said they couldnt identify the problem. Anyone have any advice of what this could be?

 

Experienced that before, Something transmission related i would say... i have absolutley no knowledge on auto's...