Rain overnight = misfires and rough running in the morning

So I thought the rough running was a result of my loose negative battery bolt connection:
[Battery cable bolts loose - but it is more complicated than that]

But the rain here has been insane for the last month or so ever since it got hot and humid. I have noticed that every night the car sits out overnight in the pouring rain - when I go to start in the morning, it runs REALLY rough and misfires until later on when I make a lot of short trips. If it doesn’t rain overnight, it seems fine in the morning.

Is is safe to assume that moisture is somehow (and I really don’t see how) getting inside the ignition coil, plug wire connections or near the plugs?

The fun never stops. Every time I turn the key I don’t know what to expect anymore.

Or distributor cap…

When the car is running good…get a spray bottle of water and start spraying ignition components until it’s NOT running great. The last thing you sprayed is probably the culprit.


My guess would be cap and rotor, but test as Mike said. If they’re old, I’d replace them and the ignition wires, regardless

1 Like

DJ44 , I have asked this question before . If this is the 2001 Cavalier you have 4000 threads about why do you not replace it with something that won’t drive you nuts?

If you have the 2.2L, you should have all electronic ignition with 2 coils. You can try removing the coils and cleaning the mounting surfaces with steel wool. Otherwise, new coils, spark plug wires, and spark plugs.


When I was a kid, my dad had a hand-me-down 70ish Chevelle. When it rained it would do what you describe and would even shut off. He had a can of “silicone spray” he kept in the car. He would apply it to all things electrical under the hood and the car would then go. For a while. Once, while taking me and a buddy to a movie it quit on the highway (Clover leaf of Rt 128 and 93 north of Boston). He jumped out and did the spray while cars wizzed past. To that point in my life in had never been more afraid. So I agree with Volvo_V70. Maybe get a new car if it can’t be pinpointed. Not worth the safety risk.