Hey everyone, first post here on the forum... have used this site before with great success but now I am completely STUCK!

I have a 2003 F150 SuperCrew/FX4 with a 5.4L and 115k on the clock.

Recently I had a fault code for a #3 missfire and diagnosed it to the coil pack. Removed and replaced and the issue went away.

However last night while climbing a hill around my house on the freeway, pretty steep grade, while cruising at 60-65 mph the truck started to shutter, then it dropped a cylinder. The SES light came on in the same flashing manner that it did when I had the bad coil. I shifted out of gear and got to the shoulder and turned off the truck and restarted. Upon restart the code was gone and seemed to be firing on all cylinders.

I let the truck idle for a while and rev'd the engine to check that everything was good and took off on the freeway. While on a grade that was not as significant as the earlier one at 65ish mph I started to feel the engine shutter like it was about to drop the cylinder again but I managed to nurse it up to my exit.

I did the plugs about 30k miles ago but imagine that coils for all the plugs will be in my future and plugs...

Does anyone have any other ideas? I'm stumped and can't avoid hills here in Western Washington forever!

Thanks!

 

If the light is not staying on, it is most likely a low grade misfire, typically a cop (coil over plug) It would be good maintenance to replace all of them at some point. Fuel filters are only good for about 15-30k these days with the fuels we use. You would be surprised what just a single cylinder misfire could feel like.

 

I went through the same thing until I replaced all 8 coils. No issues (with the coils) since then. I got them off ebay.
They look like these: ebay link

 

Thanks for the feed back!

Plugged in a code scanner this morning knowing I was going to pull the same hill and got the 303 for a misfire on #3. This is the same code I got previously and replaced the COP... is there anything else that could be sending a misfire code on that cylinder? Would plugs be a good investment at this point? I used E3 the last time I did them and think I might go back to stock this time, what is the stock plug or equivalent?

I am going to order new COP's for the entire engine, it might be overkill but the seven others have 115k on them and I would assume could be replaced.

I am also going to do the fuel filter as good measure!...

Thanks again for the feedback! Please let me know if anyone thinks of anything!

 

First off, go back to the OE plugs. These motors will act up some with aftermarket plugs. I know first hand. Chased an issue similar to this for a month just to find it was the aftermarket plugs. Also, if you replaced the COP, make sure the harness connector was snapped back to the COP good. I also ran into this problem two weeks ago on my 02 5.4.

 

Yea, I don't remember what the reviews were on the E3 plugs. But odd that the misfire would come back to that particular cylinder. I would be more interested in knowing which cop you replaced that cylinder with. Denso iridium's and motorcraft platinum/ iridium's are most recommended plugs for these trucks.

 

Any sign of antifreeze on that coil when you removed it? The heater core lines run above that side and having the missfire come right back leads me to suspect you have a tiny leak in one of them.