Electrical issues

[4.5diego]

Break and Engine Light on after clearing a check engine code

hello I'm looking for some insight/help on 1/26/24 My check engine light came on while driving at night. The symptoms were jittering at idle, rough acceleration and car felt boggy. next day i went to AutoZone and borrowed a scanner and found out it was a P0305 Code ( cylinder 5 misfire) went to an infinity dealership ( my car is a 2003 Infiniti M45 4.5l v8 VK45DE ) just in case its necessary. According to the dealership they swapped the coil pack from cylinder 5 to cylinder 1 and the code never came back. However now my Break and Battery Lights came on at first it was flickering when i accelerated, and then it would disappear. tonight however the lights came back on and are staying on. I went and grabbed a voltmeter and the battery is at 15.7V when the car is on at idle and 15.3 ish when the car is off. and the car is back at feeling boggy however the P0305 code has not came back.

My thought process was that the issue originally was a bad alternator not delivering enough power to the coil pack on cyl 5 and that's why the misfires were happening.

But now I'm not sure :/ if the alternator is giving good readings what could be the issue? I've heard that sometimes alternators will seem okay 1 second and die the next is that the case here?

Do i have multiple issues happening or is it all stemming from one?

anyways thank you for your time in reading this and i hop i can get this resolved

Update alternator charging battery at 15.5-6 volts

[VStar650CL]

That charge level is way to high, it should be around 14.0~14.5. Your alternator isn't regulating properly.

[4.5diego]

That charge level is way to high, it should be around 14.0~14.5. Your alternator isn't regulating properly.

Yeah that explains why the battery warning light comes on after prolonged driving.
Do you think that might have caused the misfiring issue? or is that a separate issue. thank you for your help!!

[VStar650CL]

Voltage that high can cause all sorts of issues, and if the charge lamp is lighting up, it most likely means the alternator is cutting out intermittently, not just overcharging. Get that straightened out first, then chase anything which remains.