Problemas com meu Honda Accord 2000 V6 3.0 LT

Greetings,
I have a problem with my car and it is as follows, when I turn it on, it feels a small vibration and at the same time if I put the air low a lot of the march, but the march already when the car heats well stabilizes, but if I leave suddenly it ranges, some opinions that have given me is that it can be a coil because of the vibration and others tell me that it can be the valve of air compensation The area that recommend me?