Hi Guys,

2003 Super Duty with a 5.4L and 69,000 miles here. It had started raining over night here and when I left for work this morning it was light rain. After driving for a few minutes the engine developed a miss that would vary back and forth from really bad to minor. After work the miss was still there and at one point I nailed the throttle and the truck took off pretty good but the battery light flickered on a little and then when off when I let my foot off the gas. The truck has the originally battery but it starts like a champ even in the dead of winter here in Pa. A few weeks ago while driving on the interstate also in the rain, the battery light flickered on as well but the truck ran fine. Then about a week latter again driving in the rain, the truck developed the same bad miss but it went away after about 5 minutes and didn't return until this morning even though I had driven it in the rain since then with no problem. On that previous trip when the engine started missing, several minutes after the miss had cleared up, the ABS light came on for a 1/2 a minute or so and then went off but the truck continued to run just fine.

I was wondering if anybody has any thoughts about what the cause of the miss and battery light could be. Could they be related? I change the oil and all filters religiously but it has the original spark plugs, coil packs and original serpentine belt and as I said original battery. Until now the truck always ran really great.

Thanks for any and all help!!

 

Sounds like you are getting water in the wiring somewhere. It is electrical, so you can rule out engine or fuel.

 

Sounds like a coil pack is getting wet, but that should light the check engine light.

 

Yea I was thinking it may be a coil pack as well. I didn't know that a bad coil pack would trigger the engine light so thanks for that but so far no light.

 

Wow, I can't believe it. I had this same problem on my old 2003. Only mine started at about 80,000 miles. It didn't do it everytime it rained, which was even weirder..only some of the time. Mine never set off any lights though. It did it after I changed my plugs at around 105,000 miles. It would go away after a few "drives". Still ran great when I sold it. I never did figure out what it was. Sorry.

 

Sounds like water around the plugs.

 

it will be the coil on plug also called coil packs! had the same thing happen to me! i replaced all 8 and its a pretty simple job. i purchased mine from jegs and got the 42,000 instead of the lower voltage for about $315 shipped! be sure to use dialetric grease inside the boots and it should run better than new!

 

COPs do not always light a Check Engine Light, in fact it seems most of the time they do not.

Have the truck scanned, but make sure the code reader can read pending codes. You'll probably see the pending code P030X, where X is the cylinder with the bad COP. Remember, from front to back the cylinders are 1-4 on passenger side, 5-8 on drivers side.

Don't forget to inspect the boots also. It might just be a boot causing the issue.

As for the battery light, that just might be a wet serpentine belt slipping under load. When everything dries out keep an eye on the light to see if you still get a battery light.

 

I've had the same problem with water around a plug. 2001 5.4 Self inflicted after power washing the engine. It would start fine and then start missing after less than a mile down the road. Didn't trigger a CEL. Pulled COPS and found water around the plugs. Used vacume pump to dry them out. The best I could figure is that the small amount of water wasn't a problem until it turned to steam (1 mile down the road). After drying them off all was fine. I had all new COPS so knew it had to be something other than them. I'll live with dirty engine in the future. NO MORE PRESURE WASHING..

 

Totally correct. The general advice is never wash your 5.4L or 6.8L engine. Power washing is even worse.

 

i had the same problem it was number 8 cyl got wet from the cowl section took out the cop sprayed wd 40 in it blew it out with the air hose changed the pack an good to go .. even had my truck in 4 feet of water playing an it was good to go

 

No, I said water AROUND the plugs and why would you change all the cops when even 1 will rarely go bad.

 

And guess what? That general advice is not always correct. I have washed, and will continue to wash the engine bay on my v-10 when ever it needs it without any hesitation. I have used both, the hose at home and at a car wash with no problems. The only disclaimer is that you will quickly find out the maint done or not done on your engine. I replaced the plugs and boots 2 yrs ago after I bought it, and know that the boots are sealed nicely to the engine so they will not allow water in there. And that is the main thing here, having the boots in top shape, and sealed properly. When you sell to a dealer they will degrease and shine your engine bay before they resell, and not have any hesitation in doing so, and neither should any owner, minus the shiney engine spray, but that is a different story.

To the op: more than likely you have a bad boot that is letting water into the plug area, and I would suggest you inspect all the boots and change them if they look like they have any wear on them. Then make sure when changing that you seal them nicely in place. Leaving them unatended will put out your coils, which are way more than any boots.

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I tend to follow the general advice too. I usually have a moderately dusty engine bay but very rarely have any troubles. I wipe it down with a cloth every now and then but no water and definitely not a pressure washer. I'll be treating my 2010 with the same lack of maintenance.

 

have the battery checked. my hubby said that if you have the original battery in, it could have a bad cell & it's having voltage drops, which can cause the coil packs to misfire. when you are in the rain you have more voltage being allocated to other things like wipers & headlights, defroster....etc which if the battery is going bad will not give enuf volts to the packs because there isn't enuf to go round.

check the plugs too.

hope this helps!!

amanda