today I was going to lunch, stopped at the traffic lights in my VX II Calais, took my foot off the brake thinking I would drift very slowly forward as per usual except the car flew forward the tacho was up to 3.5 rpm. drove off and when I put my foot down the ride was very rough at times. Got to my destination I noticed when i stopped i moved it up to Neutral and the revs shot back up. The same thing happened Sunday morning and hasn't happened since.
Could be the IAC valve ( Idle Air Control) which controls the idle speed and is situated on the throttle body, or it could be a sticking throttle cable.