Hey guys, i have my 2000 expedition 5.4 and cannot come to a conclusion to my misfire.

It all began with a misfire on #4 (P304) about 2 months ago. Since then i have gone through a handful of steps to fix the problem:

1- Swapped out coil on #4 and it seemed to fix nothing
2- swapped plug on #2 to see how to change plug so when i go blind into #4 i can change the plug. I changed the plug on #4 aswell as the coil and it ran perfect, no CEL... but i never scanned the computer to see if it was still throwing the code just incase it was a very slight misfire
3- after about 150 miles.... the plug BLEW OUT on #2 on the highway! I had to wait an hour for the engine to cool down and i swapped it out on the side of the road,(i always have spare parts with me)
4- this then gave me a problem with cylinder #1 saying i had a misfire on #1??? How you ask?
5- i swapped and cleaned COILS and FUEL INJECTORS 1-4 to be safe and the problem seemed to go away
6- a few days later, i scanned the computer and it was giving me #4 misfire again.... at this point a wanted to drive this truck into a wall and shoot 1000 rounds at it.
7- i then REPLACED the plug and coil on #4 to no avail, still giving me a code but not strong enough for a misfire.

At this point i could only belive it was either electrial, moisture in the coil, or a sensor. I decided to bring it to my mechanic to have him look at the engine. He never charges me so its always worth having him take a look, they did nothing but a compression test and came to the idea i had a bad piston... as much as i appreciate a mechanics opinion. I never believe him the first time. For the plain fact that the engine runs good and bad when it wants to... if a piton was damaged, it would not magically work better right? So i decided to pay him to ACTUALLY check the thing out. He did the following:

8- swapped out the fuel injector and reset the computer. This worked amazingly, but idk why they swapped the fuel injector. The engine reset literally fixed my truck. They were looking for corrosion with the wiring but couldnt find anything.

after a week or so... BOOM misfire again! I cannot fix this problem and i am about to drop it off AGAIN at the mechanics. Ive been looking into suburbans and might just get one before 2018. I reset the computer again today and it stopped the VIBRATING AT IDLE but still has HESITATION with accelerating.

Any help or insight on this is greatly appreciated! I have no clue what i can do at this point, i believe it is all electrical, but no way to check that assumption.

 

To keep the plugs from blowing out, you need to torque them to 28 ft/lb. You may have to use a Timesert, once one blows out it weakens the threads in the head.

I would do a complete compression and leakdown test, and consider borescoping the cylinders while the plugs are out.

 

What brand coils and plugs are you using? These engines are very picky and tend to have issues running brands other than Motorcraft

Have you checked fuel pressure? Or put a new fuel filter on it recently?

 

the plug that blew out was #2, since then i have drove over 1500 miles and havent had a problem with #2 at all.

 

[QUOTE=Patman;5225926]What brand coils and plugs are you using? These engines are very picky and tend to have issues running brands other than Motorcraft

Have you checked fuel pressure? Or put a new fuel filter on it recently?[/QUOTE

they are duralast coils.

 

my next job was to check the fuel pressure because ive heard quite a few say they had misfires on #4 because of a fuel filter. Idk why #4 specifically, maybe because its first on the fuel line?

 

These trucks are very sensitive to non-motorcraft parts

 

You shouldn't be ignoring what the mechanic told you. He probably measure low compression on #4. Check the compression again and verify.