Technical Misfires at high rpm, sometimes 1.2 (2012)

[mario05]

Hello
I have a problem with my Fiat punto 1.2 (2012). I just bought it two months ago, so I don't know much about the maintenance history. The issue is that sometimes when the car is warm and I am driving on the highway above 3500 rpm, the engine management light comes on and it goes into limp mode. It is not always the case, and I can often drive 25 km above 3500 rpm and everything goes well. When the car goes into limp mode, I can immediately turn the car off and on again, and it works normally. I don't really know what it is myself. The error codes that came up are p0300 and p0302. Now, the garage has also reported that it had a misfire in the third cylinder. I replaced all the spark plugs and ignition coils, but that was not the problem. The cables between the spark plugs and ignition coil have also been replaced, and a cleaning agent has been added to the fuel.
What could be causing the issue? What steps can I take to see what is causing the issue?

I would really appreciate your help.

 

[jackwhoo]

Does the mil flash when fault occurs ? Or is it on without flashing?

 

[mario05]

yes the engine light was flashing.

I don't know if it has anything to do with it, but once when I was standing still after a ride the rpm was not constant. you can see it in the video

 

[AnthonyH]

Maybe the fuel injectors are blocked?

 

[mario05]

Is there an easy way to check that?

Is it possible that the misfires occur consistently after about 25 km?

 

[GrandePunto PL]

Yes. For example fuel tank can develop some pressure/vacuum during operation. Venting of the tank is faulty somehow.
Easiest check ever, if power loss occurs: you undo the fuel cap (ideally on running engine - spare key needed).

 

[jackwhoo]

Could need a phonic wheel relearn.

When was timing belt last changed?