Missing after rain?

[sloexpe]

OK So I bought a 1998 Expedition about a month ago. It is 4x4 and has the 5.4 in it with 195xxx. It has run fine since I got it. I parked it on Friday and it sat over the weekend. It has been raining here prety much all weekend. Well I got in it to drive to work today and I noticed it was missing. It is missing at idle and under light load (in overdrive and going up a hill at about 50). I was talking to one of the guys at work who has an f150 about it and he told me that his truck does it everytime it rains and that he thinks his just needs new plugs. Does this sound right? It isnt a steady miss just off and on. Please help! Any ideas on what it could be? Also Ive been planning on doing plugs on it anyway because i dont know when they were done last. Is there anything I should look out for? I think I read on here that people have issues with the threads in the head getting messed up and having to put helicoils in. Are there any precautions I should take when I change them? Thanks in advance.

 

[FordandPolaris]

That sounds like plugs to me. Water probably gets past the boot and grounds out the plug causing your occasional miss. Do you get a check engine light when it happens? You can get the codes read at any auto store if you do and that will tell you specifically which plug/COP is causing your problem.

From what I have read, the plugs like to break off in the head, threads get messed up, and they are a real PITA to get at towards the back of the truck. I have replaced all my front suspension, rear suspension, and various other issues myself, but I am paying someone to change those haha.

 

[01yellerCobra]

I believe the first gen expys use the older style plug. So the plug breaking off shouldn't be a problem. That problem is for the 2nd and 3rd gen guys.

I would put new boots on the coil packs while you're in there. There's another thread around here somewhere about sealing the boots to the heads to make sure no water gets in the holes.

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[sloexpe]

I dont get any cel's and I am leaning towards the plugs but what I dont get it why all of a sudden? It ran perfect friday and now misses like crazy. Also if it is due to the rain, how is that much moisture getting under the cop? I guess I will know for sure when it dries up.

 

[TheOnlyExiLove]

I had the same problem with mine. After it rains they like to build up moisture in the distributors. I dont know much on it but i took it to the shop and it was under 100 bucks to fix

 

[babysilk]

When i got too much mud under my hood, it was missing. If you have an air compressor then spray air at all the plugs. That dried mine out and fixed the miss, plus I didnt have to change plugs. Thank the lord because they can be a pain to even get to. Maybe thats because my expy is up in the air

 

[splintrcel]

they are hard to get out but not nearly as bad as it could be. I had my intake manifold out though when i was doing it so i got my plugs out no problem. I stripped a COP bolt so the manifold needed some work. My engine doesnt run smoothe all the time though. Some days its perfect, others it just doesnt want to idle nice. I have all new plugs, springs, and boots. It still is having this random unstableness. What stuff should i be checking for moisture. I did have 2 misfires after my engine was doused in water. this happened in cylinders 5 and 6. Any thoughts?