I have a 1989 560 SEC and it has developed a problem as it gets up to operating tempeture. When starting from a stop it seems to stutter or stumble before taking off. When it is cold the throttle response is just about instant and smooth. It will also stutter when I have coasted to a crawl and then floor the gas. It seems to take a second and then builds up speed slowly then takes off again like it was cold. Any help would be great.