I have a '96-A6QW that will stumble and stall when it's been raining hard. The car doesn't need to be driven in the rain for this condition to appear. If it rains overnight and we go to use the car the next morning, it can happen. I have checked and sprayed most of the obvious connections or plugs with cleaner but to no avail.

Does anyone have any thoughts as to what I should look at next??

Thanks,

Jon

hopefully when air moisture is high, and look/listen for arcing. You may see arcs from the wires to the engine.

The stumble can happen and then all of a sudden the engine will catch and begin running just fine. Then at a light, when getting on the gas it will stumble (sometimes stall) and then run fine.

This only happens in the wet.

wires should meter at approx 6k Ohms. In my experiences with moisture related problems has typically been ignition systems. How about the wires from the coil pack(s) to the control unit? Connected, pinched?