51sparton

It seem to missing when I first start it up... I have replaced plugs wires o2 sensor and had two mechanics look at it. One mechanic found nothing wrong. Took it to Cork sport here in Portland they found fuel leak and replaced that part cars runs better. I spoke to the mechanic and he said that there is a drive train rumble maybe trans or driveshaft. But I still have this problem when its cold feels like the drive train problem or like its missing but worse. I'm mystified