Hi All !!
Yesterday as I was driving, the Check Engine light came on and started flashing on my 1998 5.4L Expedition.
The engine seemed to have a misfire under load.
Then the check engine light stayed on continiously.
I used a code scanner and came up with code P0304 which is the No. 4 cylinder misfire code.
I looked through the forums and this seems to be a common problem on these engines.
Can anyone advise me with some step by step instructions, on how to remove the #4 COP and replace it, as it seems quite difficult to get too.
I had to replace #3 and did all spark plugs and rubber boots as well because my mechanic said he had to pull the intake manifold and fuel lines. He's a friend and works CHEAP for me so I know he wasn't ripping me off; it's quite difficult to reach the rear cylinders behind the firewall. My 5.4 STILL misfires even after a new fuel filter (when he pulled the fuel lines he said the fuel was very dirty). Does anyone know the cause of these misfires?
back to the original post. I have the same problem! I even swapped #4 with number 1 and still had the problem. Changed the plug....still same problem but now I can't get an engine light or code to come out even with a serious misfire goin one almost all the time! Any ideas?
There is other issues that brings up these codes and they not spark related, I have seen this twice in 2 years, just completed a job like this on a 1998 5.4, get ready to dig deep into the pockets, the valves are pulling the stems out of the back of the valve facing, leaving the valves overall longer and the camshaft rocker arms are bottoming out the hydraulic lifters keeping the valves open, hence codes p0301-p0310 engine missfire, run a compression test on that cylinder to see this for sure. you may also have a plugged injector on the back side in the injector filter.
Hope this helps, Broken wire
I've been working on mine all week now. New plugs and coils. Fixed it for a few days the it started missing again. compression is good and can't seem to find a problem. Its got to be something easy but can't find it.
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