My 1998 Volkswagen Jetta GLS (60K miles) dies when I drive it in the rain. All other times it works great, but the minute it starts raining (or rather a couple of minutes after it starts), the engine sputters and I can’t keep the rpms up … until finally it just stops working (electrical system works fine). Once it dries out, it works fine again. Obviously something is getting wet that shouldn’t, but don’t know what or how? Any ideas?
The most common cause of this is probably old spark plug wires that get wet/damp & start arcing (so the spark ends up where it doesn’t belong). Other parts of the ignition system would also be suspect (e.g. coil(s) and wiring). Another possibility is a crank sensor that is getting too wet & allowing moisture to get at the electricals. Check splash shields under the car and wiring/harness/connector for the crank sensor.
I believe that VW has a TSB (technical service bulletin) out on this problem. They install splash shields. Check with VW regional office, customer service. Have your VIN handy.