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2001 Expedition misfire, please help!!

3K views 4 replies 3 participants last post by  r-clar 
#1 ·
I drive this vehicle about 100 miles on the interstate atleast twice a week. Last October, I was riding down the interstate and my "service engine soon" light was flashing and the vehicle was shuddering really bad. I had the code read at o'reileys and they told me it was a cylinder #5 misfire. I replaced the coil and nothing changed, so after some thinking i changed the fuel filter. I was thinking that since the problem only happened at interstate speeds and maybe the filter was clogged? Did not fix anything, it added problems. Now the truck shakes terrible at idle. If you get over 1,500 RPM then everything smoothes out. Next thing was the service engine soon came on again, except this time it showed a #4, #5, and #7 misfire. So I looked it over and the #7 coil was not bolted tightly. i tightened that up and still wasn't sure what to check on #5, so i just decided to change all the plugs. When i pulled #4 spark plug, this is what i saw

So after replacing all of the spark plugs, nothing was fixed. I gave up and took it to Ford and asked them to diagnose the problem. $100 later, they told me that my #7 coil needed to be replaced, and that i had low compression in the #4 cylinder most likely from a "cracked insert". I replaced the #7 coil and with the new coil and plug, it still doesn't effect the idle. You can unplug it while its running and it doesn't effect the way it runs. I pulled the #4 plug again and luckily the insert came out with it, i replaced it and got it all put back together and nothing changed. It is obvious that #4 is blowing oil / gas out the spark plug hole because the boot on the coil is soft and soaked with whichever fluid it is. So after some thought i got a picture of the #4 cylinder spark plug hole, and it looks like this.

and in the same cylinder,


Sorry for the long post, but I am completely stumped on this one. If anyone can help figure out what this is, that would be great. I really don't want to have to pull the head, but if thats what has to happen then that is what has to happen.
 
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#3 ·
I believe there are 203,500 miles on the vehicle. The compression test was done at the ford dealership i took it to to have it diagnosed and all they could tell me was that cylinder #4 had half the compression as the rest of the cylinders. There is an insert on the 4th spark plug that they said was leaking and that was the compression problem, but i changed that and nothing changed. I got a compression guage today and tomorrow i plan on seeing what the problem is. Do you have any idea what im seeing through the spark plug hole? Is it valves that I'm seeing, or does it look more like something in the cylinder? It doesn't smoke, so I'm hesitant to say that it had piston ring issues, and it doesn't back fire so im also hesitant to say there are valve issues. That only leaves me with a cracked head, right?
 
#5 ·
I doubt it's a cracked head. The only way to tell is verify low compression after replacing the cracked insert. If still low can use the compression gauge adapter and shop air supply to put air in the cylinder. Make sure valves for that cylinder are closed and put air in cylinder. Listen for your leak. Either intake,exhaust or piston rings. You are still at the early stages of diagnosing this. The way that plug looked it's defiantly not a good sign. And you can really see much in the hole in your pics. As stated above could rent a bore scope and look around inside.
 
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