Why does mg engine misfire while its raining?

Needs a GOOD tune-up!!.. Spark plugs.. Spark plug wires.. AND Quite possibly the coil pack!!

Not true I had the same problem and it didn't work my van still misfires and now it won't start at all

Your PCM module ( also referred to as the computer or brain ) is wet Ford issued a service bulletin explaining how to fix it. It's easier to go to YouTube and searching videos of freestars with wet pcm.

I went down the list of things it could be when my 05 freestar 4.2L was having symptoms like this I started at the top n had pcm reprogrammed twice basically ran down every wire one by one trying to find a fault in the wiring somewhere changed the crankshaft position sensor twice and the camshaft position sensor twice a few other smaller things it might have been before I finally gave in and took it to a shop I New I could trust and come to find out they replaced my ignition coil and I believe the camshaft position sensor 1 more time because with all the testing and trial n error caused the it to fail and this was 2012 every so often she sounds rough and out of nowhere spits n spiders for a sec n it shakes it off n keeps on trucking as of the 26th of feb 2018 haven't had that issue again and let me say to all you freestar owners of this particular year and engine was the only diagnosis I wasn't able to figure out on my own since 2010 when I got her I'm not technically at the professional level mechanic just yet but this particular vehicle instilled the most important information and taught me so many lessons that only come with years of exsperiance have in different makes n models throw the same symptoms at u and u find that 3 separate vehicles had 3 separate issues it's why this field will have you hooked or not even wanna ask anyways I'm heading off topic this particular make and model had some very major issues that would occur quite commonly and not only major part and engine labor intensive sum of the most costly to have done but there are some out there that'll give you your money's worth n then some if u put just minimal effort to keep up with her maintenance I am just about out of parts on it that will need replacing over the life of a car can in the 8 years I have had her still my opinion risk is way worse and likely then reward but hey if ur already passed that point and are out of things to try look me up pretty sure I can point u in the right direction