I have an 87 jetta it hesitates/sputters. Initially it only did it an the interstate when accelerating, once the car had warmed up. It would only do it after it had warmed up, and if I let off the gas some it would smooth out, but be slowing sown on the interstate, then eventually clear out and run normally. I thought it was the fuel pump, so I replaced that and the fuel filter. That didn't fix it, still does the same thing, but now it sometimes hesitates on acceleration from a stop. Since replacing the fuel pump twice it ran as above, but when in neutral idled at 2000rpm then I parked it and it died and wouldn't restart. Also, the previous two times I drove it when the temp was below freezing it ran without any problems at all. Then today it was a little warmer, and the problems returned. Any ideas?