Why Does Your Car Misbehave In The Rain?

Any mechanic will likely tell you that intermittent problems are often the most frustrating to solve. These problems can come and go, sometimes seemingly randomly, making them notoriously challenging to diagnose effectively. Even worse, it can be hard to confirm that you've genuinely solved the problem when you can't determine the conditions that caused it in the first place.

While dampness issues aren't entirely random, they can be almost as taxing to resolve. Keep reading to learn about three likely causes and what you need to repair them permanently.

1. Failing Distributor Cap

If you drive an older vehicle, your car's ignition system may still use a distributor to handle spark timing. Distributors are relatively simple components that include a rotor that spins and supplies spark to each spark plug at the proper time. The distributor cap fits on top of the distributor to protect its internal components from debris and moisture.

A failing distributor cap may no longer provide an adequate seal, allowing moisture to leak in. Depending on the severity of the issue, this can cause your car to run poorly, stall, or fail to start when the weather is damp. In most cases, replacing the distributor cap is enough to solve the problem and prevent your car from acting up the next time it rains.

2. Faulty Coil Insulation

Depending on your vehicle's design, it may have a single ignition coil or separate coils for each cylinder. If your car uses a traditional ignition system, you'll have a single ignition coil that sends high voltage to the distributor. Modern vehicles typically use coil-on-plug (COP) designs, with individual ignition coils above each spark plug.

Faulty coil insulation can cause arcing when moisture comes into contact with the part, preventing it from effectively triggering the spark plug. This situation can cause your vehicle's engine to stumble or stall. If the coil is wet enough, you may not be able to start it again. For COP vehicles, your mechanic will need to identify the faulty coil before repairing the problem.

3. Wet Mass Air Flow (MAF) Sensor

Your car's MAF sensor meters the amount of air entering the engine so the computer can make appropriate adjustments to the air-to-fuel ratio. Incorrect data from the MAF can cause lean or rich conditions, causing your car to lose power, run poorly, or stall. Faulty wiring insulation, incorrectly installed aftermarket air intakes, and physical damage can allow the MAF to pick up moisture.

MAF sensor problems may trigger several engine error codes, including P0101 (MAF Circuit Operating Range Problem). If the MAF appears to be your issue, your mechanic will first need to determine why moisture affects the sensor before repairing it. In some cases, you may only need to replace a damaged wire or adjust the air filter.

Contact an auto repair shop for more information.