Changed the fuel filter, had the tranny serviced. Double dosed the fuel with STP $7 injector cleaner (made with jet fuel, ya know...) Still occasionally misses. I am at my wits end. Maybe a second coil is going bad. Definitely imporved, but not gone. Went four days without a miss, even with me setting it up to fail. Any more suggestions???

Thanks...and keep the ideas coming!

 

Make sure that your spark plug wires aren't crossed anywhere.

 

I can only described what worked for me. When I was pulling coils, I blew out each spark plug hole with an air compressor tube. I wanted to be sure nothing including moisture was in those holes. After I was sure they were clean, I replaced the coil with a different cleaned with compressed air coil. I'm going back to read your original description and see if it was similar to my missing problem.

 

Your description, miles and vehicle are almost identical to mine. My missing has never returned. If you had two missing coils, I can see how that would compound the problem.
If you want to send me one or two coils at a time, I'll put them in my truck and test them. That's about all I can offer. If it doesn't miss for me it shouldn't be a coil.

 

After doing a little searching on this site, I have seen some people disconnecting the EGR valve and the problem went away. That probably makes it run a little richer. I wouldn't suggest replacing the EGR valve, since that didn’t' seem to fix their problem. In their case the controller was opening the EGR valve too far. This can get a little expensive shot gunning the problem. However I like the challenge (sometimes)…and it still could be another coil.

 

Three days now, no miss. I am still skeptical. Trying to get it to miss every time out. Heading on vacation on Saturday. Maybe its all OK. I'll reply when I get back...Thanks for all your help...

 

Did you finish rotating your extra coil around to see if it was one of the coils?

 

I also have almost exactly the problem you guys are describing. I have a '98 Expedition, 5.4 4WD for reference. It has about 110,000 miles. Recently I had the usualy #4 coil fail completely. I replaced it as well as the spark plugs. It ran fine for about a month, then it starts this miss on what is a typical uphill load. Part throttle acceleration and I get the miss about 50% of the time. Maybe it is me, but it seems to happen more often when the fuel level in the tank is lower, and the weather is hotter.

I intend to replace fuel filter because it should be reaplaced. If that makes no differance I will next pull the plugs out and look for problems. I suppose my next bet is going to be to replace the coils one at a time playing musical coils. I will followup with anything I find.

 

Is it possible that there is water in the fuel.
Might try some drygas.
This will make any engine miss on a random basis.
The older engines had a two line fuel system and circulated the fuel.
These one line systems could get a load of water that wont go away until the injectors pass the fuel through.

 

running great right now. I'll put about 1000 miles on it over the next week, we'll see how she does. No misses for nearly 48 hours Going on a 3 hour tour tomorrow. we'll see how she acts for a trip down I-81...

Thanks for the help.

 

Rockinport, so the solution was the fuel filter and the injector cleaner? That is the thing that seemed to solve it? I am going to try those things anyway. I will do them first and see how it goes.

 

Sure seems that way. That was the last thing I tried. I think that I may have had a couple of issues. The coil absolutley made a difference. After I installed the coil in #4, the miss went away for 4 days. Right now, though, all is running OK. I'll report back next Saturday night.

Good luck.

 

Thanks I will let you know how mine goes. I don't know if I mentioned it or not, but I had already replaced the #4 coil on my Expedition. It had failed all at once and completely. I replaced it and the plugs. About a month later it started this new problem.... on the new plugs...

 

Autozone will scan for you I think for free, Mine was misfire #4 cylinder and changed the coil and runs perfect light even when out on its own. Dealer told me #4 goes out more because heater hose line is above it and will drip down and burn it up. Worked for me, good luck....access

 

OK, I'm back...Mixed results. On the 350 mile ride out, it only misfired once. After light use for a couple of days (< 5 miles a day), I took it out on teh beach and pulled a couple of SUVs out of the sand. The 10 mile trip back to teh house, it missed a bunch!!!. Missed some on a 35 mile ride to the mainland. Leaving this morning, it missed in heavy traffic, but started running great after I got on the open highway. This is frustrating...

I'm going to try some more cleaner, and I think that I'll dielectric the boots again.......