My 1985 MB 190 runs good until it rains and the air gets saturated. Then it will barely start and will barely run until I drive around for awhile. On clear days it will fire right up and run like a Swiss watch. Can anyone give me some suggestions on what's causing this?

Check the basics, more than likley the cap, rotor, and plug wires need to be replaced.

Thanks, but that's too obvious....They are all new. Anyone else ever experience this problem?

check to see if your overvoltage protection relay (ovpr) is failing to provide voltage to the engine control systems, when acting up test for the 5v ref at the throttle plate sensor, connect dvom to pin 1 and pin 3 and measure the voltage with key on. if no voltage suspect the ovpr to have failed. the relay is behind the battery with the clear plastic cover on it. Perfect place to get wet if the large black coverings are damaged or missing.

Thanks Eclass. Best answer I've recieved yet. I'll do that next time it rains.

Does it act up if you get the car wet with a garden hose or go in a car wash? That might save you some time.