Hello, I have been chasing a misfire for months now on my C7 h/c/i. Tried replacing spark plugs, wires, and coil pack. Someone suggested it could be a bad injector, so I replaced all the LT4 injectors. The car has a 32% fuel lobe, lt4 HPFP, lt4 injectors.
It will happen randomly on the street during pulls from a roll, but at the track it happens just about 100% of the time.
My tuner suggested it could be too high of fuel pressure and we tried lowering the high pressure desired down from 20 to 18. I didn't get a chance to test this setting at the track, but I was able to do a lot of 20-120 mph runs last night and it did not misfire. However, as I understand a setting of 20 is just stock LT4 settings so I am still very skeptical that the issue is fixed. Also, the car was fine for a year with those original fuel settings.
This all seemed to start when I swapped to the BTR conical valve springs, so another idea was to just put the old springs back on that cylinder and go to the track again. Although, I also ran plenty of perfectly fine mid 10 second passes with these conical springs, so I don't know if it is that either.
Attached both tunes so you can see the fuel pressure difference. The misfire starts at 01:16