Read Apps can affect Mac performance, battery runtime, temperature, and fan activity - Apple Support.
Please determine if the problems also occur in "Safe Mode":
- Safe Mode or "Safe Boot" is a troubleshooting mode that bypasses all third party system extensions and loads only required system components. Read about it: Starting up in Safe Mode
- You must disable FileVault before you can start your Mac in Safe Mode.
- Starting your Mac in Safe Mode will take longer than usual, graphics will not render smoothly, audio is disabled on some Macs, and some programs (iTunes for example) may not work at all.
- Merely starting your Mac in Safe Mode is not intended to resolve the problem, it's to observe its performance without certain additional components.
- To end Safe Mode restart your Mac normally. Shutdown will take longer as well.
Reply with your observations.
If the problem continues to persist reset the SMC. To learn how to do that read: Resetting the System Management Controller (SMC) on your Mac - Apple Support. Anecdotal reports also indicate an NVRAM reset may resolve the problem: How to Reset NVRAM on your Mac - Apple Support. Also, if FileVault is actively encrypting the startup disk, wait for it to finish.
Other causes for a runaway kernel_task may be a faulty hardware sensor. Those causes may be diagnosed using Apple Hardware Test, though only a report of a specific failure can be considered a conclusive result: Using Apple Hardware Test - Apple Support. If you cover the Mac with cases or "skins" while it's in use, including keyboard covers, don't. Any other obstructions to cooling efficiency should be avoided also. Read Mac notebooks: Operating temperature - Apple Support.
Uninstall "CleanMyMac3". Read below.
To remove CleanMyMac 3 itself, use its Uninstaller module, followed by these additional steps:
Remove the file ~/Library/LaunchAgents/com.macpaw.CleanMyMac3.Scheduler.plist
- To navigate to that file, copy and paste the following line into the Finder's Go menu > Go To Folder...
~/Library/LaunchAgents/
Locate the following file and drag it to the Trash:com.macpaw.CleanMyMac3.Scheduler.plist
- Then, open (Apple menu) > System Preferences > Users & Groups > Login Items.
- Select the item CleanMyMac3 Menu
- Click the [—] (minus) button.
- Restart your Mac.
Beware that reinstalling OS X alone will have no effect on either removing CleanMyMac or reversing the damage it is capable of inflicting upon a system. To recover from the effects of having used it to modify OS X, the additional software you require and the essential files you need, follow the applicable recovery procedure below:
- If you have a backup that you created prior to using CleanMyMac, now is the time to use it. For Time Machine, boot OS X Recovery, and at the Mac OS X Utilities screen, choose Restore from Time Machine Backup. Choose a date preceding the installation of CleanMyMac.
- If you do not have a backup that predates the use of CleanMyMac, create one now. To do that read Use Time Machine to back up or restore your Mac.
- The recovery procedure will require that you erase the Mac using OS X Recovery, and then create a new User Account whose contents will be empty. You will then be able to use Setup Assistant to migrate your essential documents including photos, music, work products and other essential files.
- To erase and install OS X read How to reinstall OS X on your Mac.
- Follow the instructions in that document under Erase your drive and install OS X.
- Then, follow the procedure in Move your content to a new Mac.
- When asked how you want to transfer your information, select Transfer from a Mac, Time Machine backup, or startup disk.
- Under Select the Information to Transfer, select only your previous User account and do not select "Applications", "Computer and Network Settings" or "Other files and folders". De-select those choices.
- Subsequent to using Setup Assistant, you will need to reinstall the essential software you may require, once again remembering to install software only from their original sources, and omitting all non-essential software.
- "Non-essential software" is a broad category that includes but is not limited to third party "cleaning", "maintenance", and "anti-virus" products.
