My 98 Jetta will sart, run a couple of miles then lose power and die. The lights and stereo still work. It will start back up only to die again, eventually not even starting at all. This has only happened in the last two months twice, both times it was warming up and raining instead of snowing. In between it runs fine. I've changed the spark plucgs and distributor cap and wires and ingnition coil and i'm not sure what else to do...I'm a single mom with limited time and a limited budget.....help!!!!!!!!!