imac 2017 freezes due to high kernel_task cpu usage after installing sonoma through opencore legacy patcher

This has been around for a month. I have an imac 27'' 2017 and I installed sonoma using opencore legacy patcher. I did it following the tutorial, and installed the new system from a usb disk. The system booted successfully and run smoothly for a while, and then the kernel task jumped from less than 10% to 200-300%. I quickly downgraded the system to ventura and removed the opencore patcher, but the kernel task still jumps to 200-300% intermittently. Sometimes after I leave it for a day or so, it miraculously goes back to normal, but after a day or two the problem shows up again. I have tried cleanning the fan, resetting smc and nvram, disabling kext extension, but all in vain. I called the genius bar and local authorized repair store but they have no conclusion either. I wander if this is worth repairing (nearest genius bar is like 100 miles away), or I better just trade in this old machine.

submitted by /u/Sad_Cardiologist952
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