I am an owner of a 1991 560SEC. It just hit 150,000 miles this week. For the past few months, Ive been having numerous problems. Most of which seemed to happen the day I installed new spark plugs. 3 major problems, some not so bad. For one, my car will NOT start without starter fluid. The only time it will start right up is when it has been driven within the last hour or so. I haven't done much to fix this cause I dont know where to begin. I replaced all the spark plugs and the fuel filter. Neither helped. In fact, after installing the new spark plugs, my car doesn't seem to be running on all its cylinders. It shakes and putters like a boat; has horrible acceleration and has lost a lot of HP. Those 2 problems are really aggravating me. The when I try to accelerate fast, it revs up high and slams into the next gear. I bought the car at 142,000 miles and it was very fast and very powerful. Shifting fine, no mechanical problems aside from the idle control valve. Now I'm scared to bring it at anything over 80mph. Shakes the whole ride and has even started stalled a couple times waiting at a light. I really need someones help, I'm at a loss. Kinda tight on money, and don't wanna pay the big expenses at one of these local shops. Please, if you can suggest a solution to any of these problems, it would be greatly appreciated. So to sum it up; car isn't running on all its cylinders, won't start without starter fluid, loss in acceleration/power, revs high and slams into gears when accelerating fast. thanks again