Why does my 2001 ford expedition run terrible when it rains.
It could be a sensor getting wet or the fuse box getting wet mass air flow sensor fair-0 to sensor reviews -0 2 sensor reviews box mass air flow sensor
It could also be the thermostat sensor where to pick up lines in your gas tank
I have a couple of these engines and I can tell you from experience it is almost certainly a coil going bad or moisture that has accumulated in the spark plug well which shorts out the spark to the engine. You need to remove the spark plugs and probably replace them while you are at it, Dry out the well and then use dielectric grease to seal the coil boot to the spark plug which will keep moisture out. The grease can also be applied to the seal that is supposed to keep moisture out of the well. Be sure and use anti- seize on the spark plug threads when installing them into the engine,
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