I have a 95 F150, 302, auto/od 4x4, 75,000 miles. The engine stumbles or hesitates when run first thing in the morning, but only after rain or heavy fog the night before. This is usually 3 in the morning. This never happens whe coming back home, even with heavy rain, seems like its only when not running for more than 12 hours. After the engine runs(about 5 miles) it will straighten up. Sometimes on acceleration the shaking is enough to rattle the entire truck, also I noticed the tach goes a little crazy when this happens. I read somewhere about these trucks haveing wiring harness problems that short when they get wet but I have no idea where to begin. Anybody know what the problem could be? Check engine light never comes on.
Thanks for any help in advance.
Btw.. Air filter, exhaust, chip,which mod first for performance and maybe some mileage?

 

Look at your spark plugs and see if there is rust around the insulator. You mentioned the moisture in the mornings and that reminded me of a hesitation problem I was having. I had moisture collecting over time cause rust around the spark plug and caused arching. This of course is if your plugs are resessed in the engine. You know, where moisture could collect.

 

Also check your distributor cap, a small crack or it may not be sealing against the distributor would allow moisture in and cause a problem.
I did the K&N and the exhaust first and liked them both, I have also gone through the engine: bored .030, crane cam, lightly ported heads, etc and I still have not installed a chip and am making a pretty good bit of power, some people love the chip others don't, I will eventually get around to it and try it for myself. So far true duals with ceramic headers and K&N filter made noticeable mpg increase.

 

if moisture is geting to the wireing harness i have heard so don't quote me but idf you unplug it and put some vasaline on it will stop moisture just something i heard once

 

after u finally get it going spray some silicone on all the elertrical components it well help keep moistrure out