Shifting problems in the rain

My car:
I drive a 1999 Toyota Corolla with just over 138 thousand miles. It is a manual transmission. The transmission itself was replaced ~4 years ago, so it is not 12+ years old.

My problem:
As the weather has turned colder and wetter I have noticed that during rain my car has trouble shifting properly. When I start it up it starts fine, but once I start driving it will seem like the clutch is having trouble catching. Often the car will run as if I had the clutch pressed almost completely in, though based upon the low pitched sound of the engine (I don’t have a tach… even though it’s a manual) I know that I’m not revving the engine really high as if the car was in neutral. The car will sort of coast along at about 10% power for a few seconds, give a couple lurches, the engine will suddenly catch and rev higher and I will speed up to match the new higher rpm. Once the engine has caught I don’t have a problem until I need to shift up, when the whole issue repeats itself. This doesn’t seem to happen in 4th or 5th gear, and by the time I reach my destination it has usually stopped happening completely.

Today the same problem happened, but it was so bad that I stalled multiple times while trying to start from a stop. When I stalled the first time, it was quite difficult to get the car to start again. Fortunately I was only at the entrance to my apartment complex so I was able to limp back to the parking lot. Oddly, going in reverse did not seem to pose as much of a problem in terms of shifting.

Again, this problem only seems to happen while it is raining out, or after it’s been raining recently. If I rambled a bit it is because I am trying to include every detail I could remember about the times that this has happened. Does anyone have any ideas?


Sounds more like an ignition problem to me.
Park somewhere really dark. With the engine idling, hood up, look for a light show around the plug wires, distributor cap and coil. Spray a fine water mist from a spray bottle on the ignition parts.
If the engine stumbles and you see sparks you’ll see where the problem is.
No need to wet things down.