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Good morning. I am a new member and I have a 2006 Lincoln Mark LT. Recently I have noticed some misfiring under accelerating going over an overpass or up a hill but running perfectly good on flat ground. Using an Innova 3130 scan tool, fuel pressure is 38.5 to 39.1, throttle position when the misfiring occurs is about 22%, coolant temp at 196*. It almost seems like a plug wire leaking but I know that it has none. Also it seems as if it may be a coil breakdown. I know that I need to replace plugs but I know not to start throwing parts at this problem. I also have studied many other P0304 posts on this forum but have not seen one like this problem exactly. Thank you for any insight into this problem.
I think that I may have found the problem. Thank you for looking at my post.
Last edited by 95Z07; Dec 22, 2019 at 08:22 PM.
Reason: Update post
Good morning. I am a new member and I have a 2006 Lincoln Mark LT. Recently I have noticed some misfiring under accelerating going over an overpass or up a hill but running perfectly good on flat ground. Using an Innova 3130 scan tool, fuel pressure is 38.5 to 39.1, throttle position when the misfiring occurs is about 22%, coolant temp at 196*. It almost seems like a plug wire leaking but I know that it has none. Also it seems as if it may be a coil breakdown. I know that I need to replace plugs but I know not to start throwing parts at this problem. I also have studied many other P0304 posts on this forum but have not seen one like this problem exactly. Thank you for any insight into this problem.
Someone will have a copy/paste with a better description of what you need to do, but you need to change the plugs with the most recent Motorcraft updated plug. It is the SP546. While you have the plugs exposed for changing, go ahead and change out the rubber boots for the COPs. The OEM COPs on these trucks usually are not the problem, so I would not change them out unless I have confirmed they are bad. After installing new rubber boots, you could swap the COP on cylinder 4 with another and see if the misfire follows to the new cylinder. If the misfire moves to the new cylinder, then its likely the COP.
If you are not sure on the process for changing out the plugs, take a look at FordTechmakuloco youtube videos on how to do this job. It's not as simple as just wrenching them out. If your plugs have never been changed before, get ready to break some plugs. I have had good luck using a compact impact wrench and a one piece spark plug socket to rip the plugs out of a hot engine and not breaking the plugs. But you have to have the right tools.
Last edited by AlleninNM; Dec 21, 2019 at 12:41 PM.
Good evening all. I had a trouble code, P0304. See the spark plugs in the pictures. Trouble solved 😁😁😁. Those plugs had a little over 150,000 miles on them. No COP problems. Plugs were hard to come out but I warmed the engine up for about 10 minutes and that made it easier to break them loose in the head and extract them. I used the carb cleaner and PB blaster method. I backed each one off about 1/8th turn, then tightened them back up. Repeatedly did that method until the plug freed up and I was able to back them out. Thoroughly cleaned and blew out each plug hole before plug removal. They were very dirty down in the hole. After each plug removal I took a rag and sprayed it with carb cleaner then took a long screwdriver and carefully cleaned the plug threads in the heads. Runs perfectly now and the engine is all original with 310,000 on it. It took about 6 hours to do this job. It’s best not to be in any hurry at all. Thank you all.
P0304 Trouble Code
