when I am coming to a stop or at a light, there is a mild vibration felt in the front seats and progresses when I take my foot off the brake. Once I accelerate the shaking stops and the remainder of the ride is fine. One technician said it was a misfire. How can I get rid of it? If I stop hard the shaking moves underneath the car from the middle and out the muffler which makes a rattle noise, also annoying. Help please.....'85 190 E