Alternator not charging correctly caused my I30 Infiniti to misfire. Before I begin here, this car has 110k but had new spark plugs 8k miles and ran perfect until my misfire issues. Occasionally it has a coil go like everyone else has learned but not like this time.
It first showed cylinder #1 misfire code so I replaced plug & coil. All seemed well but a couple days later #5 cylinder also misfired and a spark plug fixed it.
There is a small relay in the coil wiring harness that can cause irattic misfires too so I replaced it too along with #5 spark plug and while there I switched coils around to just verify coil good/bad.
No change, it misfired #5 again 3 days later with other coil on it. Another new plug fixed it once more.
At that point alternator not charging also showed up in codes. Finally!!
It's really what caused it all but each misfired cylinder plug failed , gas fouled due to no fire is my guess? NGK plugs are very tough, ran them almost 50yrs from dirt bike days.
Original coil I removed was placed back on #1 after new alt installed and still doing fine.
No coils were ever bad in my case so a bad battery, terminal issues, elect short or bad alt can all cause misfire’s on todays cars so fully check that charging system & wiring before buying any parts. Sucks chasing misfires down on these cars. Hopefully all that will vanish for many yrs. Lmao. I wish..