2004 Kia Rio Won't Start During Rain

I have a 2004 Kia Rio that when the temperature outside is 70 or above,humidity 80 percent or over and misty or light rain, but rain that has continued for a long period of time that seems to soak whatever it is that is causing the issue, won’t start. It will try to crank, but if you continue to try it will eventually smell like you have flooded it out. All of the electrical systems work, it just refuses to start. Once it has a chance to dry out, it starts again. I have taken it to a mechanic, but they cannot seem to find the issue, but of course once I get it there, it is running again.

Hoping that you guys might have some sort of idea what might be wrong with my demon car.

A common problem is that insulation on ignition wires (the ones that connect to the spark plugs) breaks down over time and absorbs moisture during rainy weather, causing the wires to short out, resulting in the car not starting.

To check for this problem, wait until dark, then open the hood and spray the ignition wires with water mist from a spray bottle. Then have a friend try to start the engine while you watch the engine. You’ll probably see blue flashes of electricity as the ignition wires short out from the moisture.

If so, buy a new set of high-quality ignition wires at your local auto parts store, or original equipment wires from your Kia dealer.

+1 to @jesmed1 . This sounds like a wet distributor cap from the 70’s. New wires should solve your problem. Not related to your starting problems, you might want to change your spark plugs while you are at it if they have not been replaced yet.

This symptom is almost always due to a problem w/ the high voltage part of the ignition system. The thing is, electricity at high voltages isn’t easily confined to staying in the wires. The air we breath, it can actually conduct electricity too, at high voltages. And it is not just the air, electricity can be conducted along the surface of an insulated wire, due to certain types of dust and dirt residing there. And all these effects happen even easier if the air is damp. So if there’s any break in the wire insulation of a high voltage circuit, anywhere, the air can short-circuit the spark to chassis ground, instead where it should go, to the spark plugs.

The good thing about all this is that the high voltage circuit represents a small part of the car’s wiring, so it is usually a simple matter to eliminate the possibilities one by one and soon solve the no-start problem. Often just twisting the wires on 10 year + old cars will show small cracks in the insulation, so you know right away those have to be replaced.

I would start by changing the spark plugs and wires. It’s probably just the wires, but why not change the plugs while you’re there? Throw in a new distributor cap, and post back please. Rocketman

I also use the troubleshooting procedure that jesmed1 uses. It works. I kept getting a “number 3 misfire” code from time to time…especially in damp weather. I started the engine in a very dark garage and discovered that the number 3 spark plug wire was bad. I replaced all of the spark plug wires and the spark plugs as well. No more CEL.

I know that all of the spark plugs and wires have been replaced in the last year. I also thought about the distributor cap, but the mechanic that looked at it said it was not that. I do believe the next thing is going to be going out and spraying with water at night and see what happens. Part of me tends to think that the mechanic just might not know what he was doing. I will for sure keep you posted rocketman, and thank you everyone for the replies.

How is the coil configured on this engine? Is it inside the distributor? Are there separate coils for each spark plug, located near the spark plug? The reason I ask is b/c one time I had a VW RAbbit that would stall every time I went over a puddle, and after many hours of diagnosis I discovered a tiny crack in the coil housing. Replace the coil and that fixed it.

Even though your plug wires are less than a year old, one may have been resting too close to an exhaust manifold…which could damage the insulation.

I would replace the cap as a diagnostic step. It will cost less than $10.

The cap could have a very tiny hairline crack that could be the problem.
Sometimes it is impossible to see these cracks.


If it has a distributor, another thing to check when it does not start is to look and see if there is condensation inside the dist cap. This can occur if the rubber seal between the crankcase and the top portion of the distributor is not sealing; also if the rubber seal between the cap and the body of the dist. is missing or breached.