Hello all!!

My truck is a '98 F-150 over a 100,000 miles, last week i was driving trough a heavy rain and then at a red light the truck started to shake like if a spark plug was failing or something, then i thought that something got wet and it will go away when it dries, next morning when i was driving to work the problem was there again but once the engine gets hot it runs fine again, this happens every time that i started the engine, it has been a week since the problem started and i beleive the engine is dry enough because it has been over 85 degrees and it is hot, the weird thing is that after driving the truck for 10 min or so the engine runs fine again, does anyone have any idea of what is the problem ? how can i fix it?

Please help.

Thanks

 

First place I would be looking at is the EGR operation for sticking open.

 

I checked the EGR and its working fine, a friend of mine told me that it could be the coil packs, my truck has one coil pack on each side but i don't want to rush and buy the coil packs without more research, i have some question, could it be that the coil pack needs to be changed even after 10 min of driving runs fine? could be something else?
Thanks

 

I assume there is no CEL?

It sounds temp related. I would check the MAF, Air Charge Temp, Coolant/Head Temp, and even the IAC.

Next time it is running rough 1st tap lightly on the MAF if the rough running doesn't change try tapping on the IAC. If neither changes anything you might have the beginings of a failing vac hose. (Temporarily collapsing)

Just my guesses!

 

My '98 ran crappy when it got wet- and every so often. It would always clear up. I ended up changing out the wires and plugs, and discovered that one or two of my plug wires had spider cracks and were "leaking" power. (The electricity was following the path of least resistance, and arcing against my valve covers- I discovered this by opening the hood at night and watching the fireworks.) 100 bucks later and it was running 100 percent better!

 

I pulled the codes and this is what i got P0303 and P0401, P0303 is a misfire on #3 and P0401 its says something about Exaust Gas Recirculation problem, last time that the truck was in the shop they told me that the EGR valve is ok, maybe it is the EGR sensor i guess, any ideas on how to fix the problems?

Thanks guys

 

It is more than likely secondary ign. related. If you have old, high resistance wires and then high moisture the spark ends up going to gound on the engine and not reaching the plug. For fun you could wait until dark and watch for the arc. I would change out the plug wires.

 

Hello guys!!

The misfire problem is gone, i found some water in one of the coil packs so i pulled out all the spark plug wires and blow them with compressed air all the way to the spark plug and pu them back and VOLALA problem gone, now i just have to deal with the P0401 code, so thanks everyone for your replys and i will post later the update with the P0401 code.

Thank you