F150 5.4L 3V Misfires

[mgarde94]

Hello, first time poster here and new to forscan. I'm trying to diagnose what's going on with my truck. It's a 2010 F150 Lariat 4x4 with the infamous 5.4L 3V engine. It's got 205k miles on it. I checked the mode 6 data and it's got misfires on every cylinder with cylinder 5 having significantly more than the others. DTC's present are all related to misfires: P0300, P0301, P0302, P0305, P0306, and P0316. It's definitely due for some plugs and coils if that's the issue but I don't think that's the issue since I've got misfires on every cylinder. It seems unlikely all the spark plugs or coils would fail at the exact same time so i think it's a system issue that serves all cylinders. What I'm worried about is it being timing related since these engines are so finicky with the timing and oil. About 40k miles ago, I replaced the fuel injectors and VCT solenoids but the other timing stuff was still working great so left it alone. I checked the VCT errors with forscan and it showed 0% on both so unless the base timing is off, i don't think that's an issue. Did another run with forscan checking the mass airflow, short term fuel trim, and long term fuel trim and i'm hoping that has narrowed down the issue. Mass airflow right after startup (cold engine) is about 14 g/s, which seems very high, while both short term and both long term fuel trims were 14-19% which i believe they should be nearly 0%. At warm temps (about 20 minutes of engine running), the MAF is about 8 g/s while the short and long fuel trims had settled down to around 11%. So it seems like i have some type of fuel / air issue rather than spark or timing. Its very frustrating there are no other DTCs to give a clue but hopefully that means its not timing related since there are no timing codes. Any suggestions if i'm going down the right rabbit hole in chasing fuel / air? Suggestions on next steps? I can send Forscan logs as well if that would help.

[DAN1000]

Fuel trims should be below 10%, a system in good shape typically runs at 3-5% + or -
Try spraying brake cleaner at parts of the intake & air inlet while watching O2 pids.
If you see any sudden o2 movement going rich you have a vacuum leak

PS: your well overdue for plugs as their rated for 100000 miles, hope you don't have the ones that break off in the head

[mgarde94]

Vacuum leak is where I was leaning. Forgot to include this but when I held the car at ~2500 RPM, the fuel trims ranged from -3% to +3%. The accelerator was also very sensitive.

[hueypilot]

Fuel trims should be below 10%, a system in good shape typically runs at 3-5% + or -
Try spraying brake cleaner at parts of the intake & air inlet while watching O2 pids.
If you see any sudden o2 movement going rich you have a vacuum leak

PS: your well overdue for plugs as their rated for 100000 miles, hope you don't have the ones that break off in the head

Yes, there are the plugs that break in the heads when removing them.

[mgarde94]

I should have clarified. I previously changed the plugs at 150k miles and I try to change them every 50k. So with 55k miles on them I consider them to be coming up due. I try to stay on top of those more frequently than mfr recommends so I don't have to change the coils (replaced at 100k miles). I can't bring myself to trust mfr recommend service intervals after they started saying things like "lifetime fluids".

[hueypilot]

Is the misfire worse at an idle, or highway speed? Does it misfire during hard acceleration? Find mode 6 on the scanner. Scroll down to test #53 or #56. This is real time misfires from 0-200, and resets after 200 and starts over again. Are all the cylinders misfiring equal in the count, or is one or two cylinders really bad?

[DAN1000]

One thing I found on these older trucks is the wiper cowl seals leak & drip water along the valley where the coils sit filling the spark plug holes
You may want to water test that area