* Ignition System: Water getting into the distributor cap (if equipped), ignition coil, spark plug wires, or even the spark plugs themselves can cause misfires, leading to a rough idle and triggering the check engine light. The misfires are directly caused by interrupted electrical signals or water shorting out components.
* Mass Airflow Sensor (MAF) Sensor: This sensor measures the amount of air entering the engine. If water gets into it, it can give faulty readings, leading to a poor air/fuel mixture, a rough idle, and the check engine light.
* Computer/ECU (Engine Control Unit): While less likely due to some protection, water can potentially damage the ECU or its connections. This is a more serious problem.
* Sensors: Other sensors crucial for engine operation, like the crankshaft position sensor, camshaft position sensor, or throttle position sensor could be affected by water. These sensors send signals to the ECU which helps determine engine timing and fuel delivery. Any faulty signal will result in a rough idle and trouble codes.
* Wiring Harnesses: Water can corrode or short out wiring harnesses, especially if the insulation has deteriorated over time. This can affect various systems and cause erratic behavior.
What to do:
1. Don't drive it further: Continuing to drive with these problems could worsen the damage.
2. Check for obvious water: Inspect the engine bay for any visible water pooling or dampness around the ignition system, sensors, or wiring harnesses.
3. Get the codes read: Use an OBD-II scanner (available at auto parts stores) to retrieve the diagnostic trouble codes (DTCs) stored by the engine control unit. These codes will give you a much clearer indication of the problem.
4. Professional diagnosis: Based on the codes and your visual inspection, you can better assess if you can attempt repairs yourself or if you need a mechanic. Water damage can be tricky to diagnose and repair thoroughly.
It's important to address this issue promptly. Ignoring it could lead to more extensive and costly repairs. The priority is identifying the source of the water intrusion and resolving any electrical short circuits before attempting to restart the engine.
