OK,

Dealing with this for 6 months. Following rain noticed rough running and check engine light. Code said cylinder 1 misfire under 200 rpm's. Replaced plugs and ran good till rain. Dry for a while and it would miss till warm 10-15 minutes and clear up- at this time no check engine light.
As of lately miss seems worse after rain. Check engine light steady on and then flashing- code read cylinder 6 misfire. Changed coil 6, engine still runs rough and check engine light only flashes not steady on. When it dries ouit it runs like a champ. Today it rained and flashing check engine light all the way to work 45 min. Probably not a good thing for cat!!! Help please.

 

sorry 2004 3.0

 

Sounds like distributor/ignition coil moisture issues. Where the spark plug wires all come together and plug into that plastic cap that looks like a petrified octopus is the ignition coil which is part of the timing system and controls the timing of the power to the spark plugs in sequence. If you are getting all those misfire codes my guess is that moisture is getting into the ignition. See a pic here Ignition Coil

 

Had the same problem. Problem coming from cyl #5. I had the whole bank of of plugs replaces, didn't feel like putting out $240 to pull the intake manifoldto replace the back set. My mechanic alsoreplaced the tubes and springs from each coil.

So far, so good. Rained cat & dogs that night, and no problems.

 

I realize this is an old post and has been rehashed many times, however, no one has touched on one item that is overlooked. Everyone talks about moisture entering the spark plug boots and getting the plug wet. Some people even swap coils to different cylinders and get the same results. Many spend lots of money purchasing all new boots, coil packs or spark plugs. Possibly the only real culprit is the electrical connector to the coil-on plug itself. If you look inside the female plug you should see a lime green rubber gasket the fits around the 2 pin connector (in a rectangular shape). Mine on cylinders 4, 5 and 6 were misshapen and pushed back from the connector, not doing their job of sealing the electrical connection. Water vapor and rain can easily get past them. From this perspective changing coils does nothing. I re-positioned the rubber seals properly before carefully pushing the connectors back on, ensuring a water, dirt and oil proof seal at that point. The boots themselves are water resistant. Also I have sprayed CRC silicone around the boots and electrical connectors and so far I have had good luck in the wet. Food for thought!

 

This is good advice. A tight seal is always good.