1999 Ford F150 70,000 miles 5.4 liter. Everytime it rains my truck idles rough. It happens even when the truck sits overnight and it rains. When I first start it up in the morning. The problem goes away after the weather turns sunny but always returns in the rain

 

might have something to do with some electrical parts gettting wet and not delievering enough spark. Im not sure...someone will know....

 

Something somewhere is getting wet. You could have water getting into the intake somewhere and causing it to run rough or water in your fuel will make it do the same thing. Is it a huge difference ? Does it run rough enough to make the whole car shake ?

 

look at the connections at the starter

 

No **** sherlocks. I know something is getting wet. Hence when it rains it doesn't run good

 

I had an 82 Bronco, 302 that would totally shut off if it rained hard
while you were driving it. Never could find out what caused it.
Marc

 

Andrew, the guys are only trying to help. If you have to take on that kind of attitude, do it somewhere else.

 

Wow, talk about an ingrate. Must be a frustrated closet chebby owner.

 

Hey Andrew

A real truck and no repairs maybe...but your plastic might work.

Plastic sheeting, that is. Why..well next time it rains..look under dash with flashlight.

Its been posted...try search...you be the "SHERLOCK"

OT

 

Andrew V,

Something might be getting wet...... Check it out.

2 suggestions;

1 Don't drive it in the rain.

2 Loose the attitude.

#1 is sure to fix it but #2 will help with any other problems you might have with it.

Regards

Jean Marc Chartier

 

I had an 83 Escort that did the same thing. It would even do it in heavy fog/mist. A guy told me to take it somewhere very dark when it was doing this and pop the hood and check the wires. Sure enough, blue sparks arc'ing on the wet wires. Ran fine when dry. Might need new wires or make sure you have them properly separated.

Good luck!

 

drm7,

Dodges with the duraspark did that too.
The 5.4 has a COP ignition. Coil on plug.

Andrew,
If it only does it when wet I would suspect 2 areas. The front of the engine where the CAM and Crank sensors are located. If the connectors are not properly seated they can allow moisture in and cause this. Or my second guess would be the inside of tha cab. If there is a leak in the windshield area it could drip on the GEM/fuses or PCM and cause this.

Is the truck stock? Any bolt on mods?

JMC

 

JMC....I was thinking that the earlier 5.4s had wires, my brother has an 02 and I know it is COP. If no wires I'm not much help.

 

Thanks for the useful tips guys. Yes it is a COP ignition and it is completely stock. I have checked unded the dash for moisture and haven't found anything wet,not to say it is not getting damp. I will check under the hood tonight. Just my luck it is pouring out,perhaps I will see some sparkin and arc'in.

 

Ive just started having the same problem with my 2006 F 150 v6, it even made the engine light come on.