I had my '78 450SL out on the road last weekend, and it ran great. I took it out today, and it idles a little rough, and when I accelerate, the car sputters but it gets up to speed. I thought maybe a spark plug was dirty or fouled so I changed them but no improvement. The engine still sputters. Any ideas or suggestions?

I replaced the ignition wires, distributor cap, and the rotor. This corrected the problem. The car runs great. I suspect that the rotor was the main problem.