DFerg95

Hey there, longtime listener, first time caller. I have a 2014 F150 5.0 with about 120,000 miles on it. Starting around March of this year I got a check engine light (P0304) for a misfire in cylinder #4. So I went out and bought 8 brand new motorcraft coils and the problem went away until about July when the CEL came back for cyl #4. I checked cylinder #4 spark plug, the plug looked good, somehow was gapped down to about .25, so I regapped to .45. I guess I should add that the plugs were brand new at 100,000 miles. So about 2 weeks ago I replaced all 8 fuel injectors with motorcraft injectors. About 2 days later the CEL popped back up, same cyl #4 miss. The CEL only pops up on startup when the motor is cold. For the most part the truck starts perfectly and idles great. The times where it misses, the startup idle is fairly rough and the motor shakes a bit, but once the motor warms up and the idle RPM comes down the truck idles perfectly. It drives great even after the CEL comes up, has no loss of power, and is getting 18 mpg on my 60 mile a day, flat highway commute. I'm at a complete loss. I've had this truck since it had 17,000 miles on it and have always done every little bit of maintenance on it. Anyone have any ideas?

Jbrown1534

are you having any other codes other than the cylinder 4 misfire? there are many things that could cause a misfire that aren't directly the plugs or coil packs.

DFerg95

No other codes at all. Every time CEL comes on its P0304 by itself.

jkenprice1

I know this is a little late, but, I think you should have taken the money you spend on all new injectors and had a dealership run an engine diagnostic. Replacing injectors on cylinders that weren't having a problem probably was not beneficial. Replacing parts without knowing the problem gets expensive really fast. There's no shame in going to the dealer for diagnostics.

DFerg95

My thought process on swapping all the coils and all the injectors was if it was one of those parts, I might as well replace all of them while I’m in there.

jkenprice1

I get that. I guess I've been lucky, my 2013 has 311,000 and I haven't had to replace any of the coil packs or injectors. I'm kinda like if it aint broke don't fix it. I had a miss with a CEL at 100.000 miles. I went to my local dealer and had them check it. Turns out I had a bad valve and ended up getting a new head. Never did change the coils or injectors. Did it hurt for you to change them. No. Was it needed? Probably not.. just saying, you probably would have been better off spending your money fixing the problem.

Kcode289

I have a 2014 with the 6.2L and had a similar issue. CEL on, rough idle. Ford dealer charged me $1300 to install new plugs and a coil on the misfiring cylinder (#8). When the CEL came on again a day later, I went to a reputable local mechanic who was careful and located a broken valve spring on the #8 cylinder, and replaced it for less than half what the dealer hit me for. The truck is past warranty, and I'm glad I now have a trustworthy and reputable mechanic. Check yr valves/valve springs on the misfiring cylinder.

I've since learned that the 6.2L, tho a good engine, has a reputation for a rough idle. Doesn't bother me as long as the CEL stays off. Kcode289

Spiky

Kcode289, you should learn how to change plugs and coils. It's not very hard and dealers charge outrageous sums that are not justified.

[F2C]MaDMaXX

This. Unfortunately, seems a known issue, but i am unsure if it's only early 5.0's, and/or when the valve material was changed to fix the issue.

Nomad8324

It was supposedly fixed from what I heard around 12 when they updated the part. That said my 2013 was down for about 6 months getting diagnosed and ultimately getting both heads replaced for bad valves. The selling dealer wanted to keep throwing parts at it instead of simple things. IE if #7 is misfiring and you switch the coil with #8 and the misfire doesn't move it is probably not the coil.

Second dealer found the injector on that cylinder was bad and replaced it. Which helped but it still had a issue. So onto the compression tests and BOOM not sealing. The fun part at the time is the heads were on backorder then months waiting to get the truck back.

Do the tuneup if you haven't but if that doesn't help get the compression tests done.