* Ignition Coil(s): Cracks or failing seals in the ignition coil(s) can allow water to penetrate and cause misfires. Inspect the coils carefully for any signs of damage, cracks, or corrosion. They are relatively easy to replace.
* Distributor Cap and Rotor (if equipped): Older Windstars might have a distributor. Moisture inside the cap or corrosion on the rotor can interrupt the spark. Inspect for cracks, corrosion, or excessive wear. Replacement is relatively inexpensive.
* Worn or damaged spark plug wire boots: Even with new wires, the boots at the plug and coil ends might be cracked or worn, allowing moisture ingress. Inspect them closely.
* Intake Manifold Gasket Leaks: Water could be getting into the intake manifold through a leak in the gasket. This can cause misfires by disrupting the air/fuel mixture and affecting the combustion process. This is less likely to be directly caused by rain, but worth considering if you notice water accumulating in other engine compartments.
* Wiring Harness Connectors: Look for any exposed wiring connectors or splices, particularly near the engine. Water could be entering through damaged insulation. Inspect closely and consider sealing any vulnerable areas with dielectric grease.
* Sensor Issues: While less likely to be directly influenced by rain, a damp sensor (like the crankshaft position sensor or camshaft position sensor) could be malfunctioning, causing erratic ignition timing and misfires. These sensors are often located in exposed areas.
Troubleshooting Steps:
1. Visual Inspection: Thoroughly inspect all ignition components, looking for any signs of moisture, damage, or corrosion. Pay close attention to the areas mentioned above.
2. Test for Spark: Use an inline spark tester to check for a consistent and strong spark at each cylinder. This helps isolate if the problem is in the coil, wires, or something else.
3. Check for Error Codes: Use an OBD-II scanner to read any diagnostic trouble codes (DTCs) stored in the vehicle's computer. These codes can point to the faulty component.
If you're not comfortable performing these checks yourself, take your Windstar to a qualified mechanic. They have the tools and expertise to diagnose the problem accurately and efficiently. Be sure to explain the problem only occurs after rain to help them focus their diagnostic efforts.
