this is a problem ive been chasing the entire time ive owned this car the last year and at this point i just dont understand.
the problem: when i start the car, regardless of whether it's a cold or warm start, i will get misfires on one to all four cylinders. sometimes i will go away for awhile, the longest it was gone was around a month last summer, and sometimes it will be every single start. the only thing i can link to the issue is that it seems to fire up perfectly when the weather is warm, and start horribly when the weather is cold. after it starts up it smooths out in around 10 seconds at the max and from there on i have absolutely no more issues. it idles perfectly, drives with tons of power, you'd never know. on startup i never see any fuel pressure issues, however for some reason it seems to actually read more fuel pressure from the in-tank pump than it should be getting. around 100psi rather than 70.
what i've tried in the last 10k miles at the maximum, all OE or OEM parts:
timing chain
fuel filter
hpfp
plugs and coils (multiple sets)
valve covers
vanos solenoid
checked for vacuum leaks (none)
checked for unmetered air coming in (none)
injector cleaner (hail marry attempt)

i've done many others things to the car in terms of new parts etc, but those are what ive tried to fix this issue from what i remember. i truly have no idea what could be the issue at this point. all i can think is maybe an injector issue, but those seem fine considering it runs perfectly otherwise. i've thought its perhaps a bad cylinder or a few, but that doesnt really explain why it keeps moving cylinders all the time. its been cylinders 1, 2, 3 or 4 or a combination of them. i really have no idea, has anyone had an issue like this before? again, the only thing i can seemingly link to when its bad vs good is the ambient temperature. could it be something like the temp sensor in the themostat? i doubt it considering it always gives me what seem like accurate temps, but i have no idea.

 

i may have solved the issue, so far it's been 3-4 days and hasnt happened so heres what i did in case anyone else is trying to track down this misfire issue. unfortunately im not really sure which of these things actually made the difference or if the issue wont just come back
one - made sure my coil packs have a perfect ground (tested with multimeter)
two - replaced in tank fuel pump. my fuel pressure read fine on startup before replacing but it has made a noticeable difference, especially in how much the engine cranks before firing. somehow maybe air was getting into the old unit? not sure