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Q: Unable to start after it rains or misfires until the engine heats up in high moisture conditions

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After a heavy rain the van will not start it will turn over but not fire. If there is a heavy dew in the morning or a fog situation it misfires until the engine heats up after that it runs fine. I thought the hood gasket may be worn out allowing water in the engine compartment so I replaced it and the problem persisted. I cleaned the Mass Flow Valve with the spray they make for that and that didn't do it either. Is there another sensor that I should be looking at?

My car has 115000 miles.
My car has an automatic transmission.

Hey there. This misfire no-start in wet or damp weather is going to be caused by the ignition system of the engine. In order to isolate the cause you can remove the inside engine cover and then start the van.

Watch the ignition wires, coil, and coil wire for arching while using a spray bottle with water to spray a fine mist of water on the ignition system in small areas at a time to find the cause of the engine misfire and you will get a misfire or stall when the spray then causes a miss. You most likely will have an ignition coil and plug wires that are arching to ground. After the cause is found, then I would recommend replacing the distributor cap and rotor, plugs and plug wires and the the ignition coil. This should repair the problem for you and the engine will run better altogether with a fresh tune-up.

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