2009 Pontiac Vibe - 1.8L engine (2ZR-FE)
I have unfortunately reached desperate measures but I am hoping someone may have a possible logical answer
Here is the story, when the car has been sitting for longer than 4 hours when the car is started it pretty much sounds like the engine is chocking, rpm will go to 1.5k then 1.1k then back to 1.5k, and so on for maybe three, or four times (Which is very abnormal since its never done that)
The check engine light gives a P0304 code, meaning it is a misfire in cylinder four, I have swapped the spark plugs, the misfire has not moved, I have swapped the ignition coil and the misfire has not changed position.
What is interesting is the engine started with a P0300 code and after two weeks it switched to a P0304 code and has been ONLY showing that code since then.
The MAF sensor has been cleaned too.
There is also a small engine rattle, which almost sounds like two utensils knocking on each other and the sound is repetitive faster ONLY when the throttle is applied and the sound is still apparent when the serpentine belt is removed too. When the car is idling the rattle is not there, and it will ONLY happen when the rpm is past 2.5k with throttle applied.
Engine oil and coolant levels are topped to the proper level, the engine does NOT burn coolant or oil!
Check engine light will turn on due to misfire on cold start but goes away when the engine warms up (after three start cycles or close to that) however will turn back on whenever the car misfires during the cold start (when it has been sitting longer than four hours)
To give further context, the outside temperature is -5 degrees Celsius, sorry my Americans ahaha anyway the colder it becomes the more apparent and severe the misfire is until the engine is warmed up then it seems to go away, or at least the engine stops jerking do not quote me on it.
UPDATE:
Replaced all four fuel injectors and the misfire still happens.
Compression test result (8 engine rotations from the starter):
Cylinder 1, 120 Psi
Cylinder 2, 118 Psi
Cylinder 3, 118 Psi
Cylinder 4, 114 Psi
I have uploaded a video of the cold startup on my channel:
https://youtu.be/zaUiZacz20Q