I own a 97 chevy astro van, for the past two months the "Service engine" light goes on when it rains and the van's engine misse at idle speed, kind of hesitates or stumble during acceleration, after I drive it for a day or two after the rain, the light goes off and the van runs smoothly.
I changed the gas cap, thought that would be the problem, but it happened again last rain.
Sometimes it sound like a vacuum leak under the car.
anyone has an idea of what is causing this problem, or has had the same problem before?
thank you in advance