Cylinder 6 misfire issue

[Matt Jackson]

I have a 2014 5.7hemi, done approximately 146k miles. Developed a miss fire in #6, done the plugs and coil swap, started up and was making a tapping sound (no tapping sound before just rough), reved it and it went away but comes back on idle. Thinking it’s the mds solenoids so went to work on that. Got it stripped down for swapping those out and put rags in the intake holes while intake was off. Had to stop at that point and call it a night. Accidentally remote started the truck at this stage, nothing happed and shut it down turning over quick. However did notice that all rags stayed in the ports apart from #6, is that a massive coincidence or is there a deeper problem here? I don’t want to do the solenoids, put it all back together only to have to take it apart again. On a side not I did find that the harness going to the solenoids was not good and melted to the top of the engine so going to replace that as well.

Codes I got when noticed the miss fire were u1449, P0306 and P1416. I got these before I did anything to it.

 

[Black-Wolf]

Might be a cracked cylinder head. Old school way to test, is you need to have someone turn the engine over while the spark plugs are disconnected, put your thumb over one of the spark plug holes for #6 (put a plug in the other one) and see if you feel pressure while the engine is turning over. Compare it to a different cylinder using the same method. Watch your hands and stay away from any moving parts! If you don't feel significant repeating pressure during crank, you definitely have a serious engine problem. If you feel pressure, but it's less than the other cylinders, you may have a minor crack. If it's a cracked head, you can rebuild the engine and just go ahead and do some mods while you're at it: MDS delete, 6.2 cam-shaft, new push rods, new piston for #6 - probably a few other things. - but whatever you do, DO NOT USE A SEALANT - there are companies out there that will tell you it's ok to use a sealant, but it is a very TEMPORARY fix at best! At worst, you'll ruin that engine for good! If you have good pressure, your problem could be a clogged injector port or lack of air/fuel mix getting to the cylinder - so check your fuel rails. Also google the codes above or take a look here: https://www.obd-codes.com/p0306. The other two codes U1449 and P1416 don't make a lot of sense for a cylinder misfire. More than likely, at least one of them is a separate problem. Diagnose based off the P0306, fix that, then if those other codes don't self resolve, diagnose and fix based on P1416, then lastly, on U1449.