I am new to this so be gentle, I have a 1997 f-250 with the 5.4. I had a coil go bad 6 months ago so a repalced all 8 with global coils, also 8 new plugs. Now about 4,000 miles later I have the misfire of the century. This started two days after my wife filled the tank up, slowly progressing to it's present state. At present it will not idle at all, cold it wants to shake every bolt loose, once worm it tames down but still won't idle and misses at any rpm randomly. Fuel consumsion is off the charts, my 700 horse latemodel is a hybrid compared to this thing. It put out a random misfire on a buddies scanner, tps fault and a failing o2 sensor. I now have replaced both and no change, also did a fuel filter change and checked for water and treated for water even though very little was found in the tank.

I need help and input, if I have forgotten any valuable info please ask. I also must point out I live in Michigan and lost my job so I can't afford this.

 

Did you use plenty of dielectric grease when you changed the plugs and cops? What kind of plugs did you put in?

 

So it idled and ran perfectly fine before the last fill up? And it began immediately after the fill up? If that is the case, it's hard not to point at bad gas, whether it's water or some other contaminant. And if it's some ignition-related, multiple-component failure then that's a heck of a coincidence.

I would be looking really hard at fuel-system related things before dropping to ignition problems as they normally happen in less-disruptive ways. Quality, delivery, and pressure should be checked, and then I would move to checking injectors that may have been plugged by contaminants.

It sounds like it's going to have to be something common to several cylinders or one bank, so after the fuel system is declared healthy you'll have to open your eyes to possible problems with the IAC and things like that.

Good luck with it, I know it must be every frustrating.

 

If you think it's a fuel issue, drain the tank, put a can of BG44K cleaner in it, and put some fresh gas in. Change the fuel filter again.

 

I will try the BG44K for sure. What is the IAC, I don't know all these acromyms for the modern fuel injected car?

 

Idle Air Controller.

Again, what kind of plugs did you put in? There's a reason I asked, these engines are fussy. Bosch and Autolite are a definite no-no.

 

Check the connections from the spark plugs to COPs. It's best to use dielectric grease on these connections.

You only used Motorcraft spark plugs, right? If not replace with Motorcraft.

I doubt it's the fuel, But I could be wrong.

Test the new COPs, you could have gotten one or two bad ones. Not likely but possible.

 

I used champion spark plugs and have always had good luck with them. If that is a no no then I will replace them fore sure. How do you test a single cop to find the bad one or ones if no code is sent? I am also certain it is not a fuel issue now I have replaced it with known good fuel with same results.

 

if the miss is bad enough then you can unplug each coil an see which one doesnt make a difference. whichever one doesnt make a difference is the one thats miss firing. some say champions are good in there trucks others dont. if you do need to replace the plugs then i would use motorcrafts for your engine.

 

The only Ford truck engine I would use a Champion in is the 5.4 3v.

 

Why? is the impedence of the Champion different than the Motorcraft, putting extra load on the coil and burning the internernal windings? Or have you had no luck with the Champion plugs? I see a lot people saying use only Motorcraft and I am not sure why. I would like to know if there is a reason for that. I have purchased a NGK plugs for my airplane before and even though they cross referenced they would not work, to much rf noise. I put in the Champion plug and perfect. It ended up being a resister Champion and non resister NGK, even though they cross referenced to each other.

 

For some reason, the modular OHC Ford V8's just don't run totally right with anything other than the OEM plugs. Some people haven't had any issues, but enough people have that it's prudent to stick with OEM. The OEM's are made by Honeywell to Ford specs.

 

ok it seems that I am able to unplug each individual coil and get almost no change, any ideas?

 

are you being serious? if you unplug one coil that is firing properly, it will miss worst and you will really notice it.

 

I am serious I can not notice a big change from one coil to the next, that is how bad the miss is! Not enough to say that coil is firing bad.