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Macbook Pro CPU problem - idle % consistently low, please help!

2452 Views 8 Replies Latest reply: Feb 7, 2013 5:45 PM by Linc Davis RSS
shesellssancturary Level 1 Level 1 (0 points)
Currently Being Moderated
Jan 31, 2013 8:04 PM



I've had my Macbook for about 8 months and never had any problems with it. Recently it started running very slow - freezing, mouse moving slow, typing response slow. I tried some solutions I found online (installing all updates, resetting NVRAM/PRAM, reindexing Spotlight, verifying disk permissions, entering purge in terminal). None of these worked. I checked Activity Monitor and the problem appears to be with the CPU, since every time the computer is running slow the Idle % is under 10%. Out of an abundance of caution, I uninstalled two Chrome plugins which were the only things I've installed in months (Adblocker and Disconnect.) I don't use any games or any other apps - pretty much all I do on my laptop is browse the internet on Chrome and use MS Word. I also have plenty of disk space, so I know that lack of storage is not causing this problem.


The only thing that has worked, at least temporarily, is shutting down, connecting to power source, and holding ctrl option shift power for 10 seconds, then turning back on (this was suggested in another thread on these forums.) The first time I did this it worked like a charm - my computer worked fine afterward, with the idle% back up to well over 90. However, it started running slow again the next day. I repeated the key process and again it seemed fine. Then again it slowed.


At this point I've tried the same solution several times and it doesn't seem to be helping anymore. Upon startup the idle% use in Activity Monitor is anywhere between 4% and 10%. The kernel_task is showing around 350% in Acitvity Monitor.


I have a very important test coming up at the end of the month and I'm studying 16 hours a day, and can't afford to be away from my computer for long. Is there ANYTHING I can do to fix this from home, or does it need to be taken into Genius under Apple care? If so, will they have to send it out and replace the hard drive, or will it be an easy in-store fix?


Any information would be appreciated! I am about sick to death of Apple products (my old first gen Macbook Air had to have its hard drive replaced twice and its screen replaced once.) If I can't find a solution I may have no choice but to up and buy a PC.

MacBook Pro (13-inch Late 2011), Mac OS X (10.7.5)
  • leroydouglas Level 6 Level 6 (13,335 points)

    How much free Hard drive space do you have?


    Did you install anti-virus,  if so which one?

  • clintonfrombirmingham Level 7 Level 7 (26,780 points)

    You don't need an anti-virus app - they can sometimes cause problems, which is why I'm sure leroydouglas asked...


    But to get back to your problem. kernel_task should not be taking up so much CPU overhead. If I were you, I would boot into your Recovery partition (holding down the Command and R keys whilst booting) and reinstall Lion. It won't damage any of your user data at all. Not the same as a 'clean' install, but, at least, it will be a 'fresh' install.


    Good luck,



  • leroydouglas Level 6 Level 6 (13,335 points)

    Have you ever 'Repair Disk' with Disk Utility? This would be booting into the Recovery partition hold the command -R on restart to use that Disk Utility. If there are errors and repaired run it again until no errors. Run the repair permissions from here as well.


    Other thoughts Reboot into SafeBoot (restart holding the shift key) log in and try your machine in that environment.  This will also clear the dynamic loader cache, font caches among others. First reboot will be noticeably longer as the cache files rebuild.


    No I am not recommending Anti-virus.

    MacBook Pro (15-inch Mid 2010), OS X Mountain Lion (10.8.2), 2.4GHz IntelCorei5 320GB HD 8GB RAM
  • Linc Davis Level 10 Level 10 (107,825 points)

    The kernel is using excessive processor cycles. Below is a partial list of causes for this condition.


    When it gets high temperature readings from the hardware, the kernel may try to compensate by interrupting the processor(s) to slow them down and reduce heat dissipation. This condition can be due to an accumulation of dust, to high ambient temperature, or to the malfunction of a cooling fan or temperature sensor. You might, or might not, see messages like the following in the Console window:

    SMC::smcHandleInterruptEvent WARNING status=0x0 (0x40 not set) notif=0x0

    The timestamps of those messages (if any) indicate the times, since the log was last cleared, when a processor was being throttled due to high temperature.

    Note that if the problem is caused by a faulty sensor that reads too high, there may be no actual overheating.

    The Apple Hardware Test, though not very reliable, is sometimes able to detect a bad fan or temperature sensor.

    Using Apple Hardware Test



    Transferring large amounts of data to or from an encrypted disk image or FileVault volume may put an extra load on the kernel. If both the source and the destination are encrypted, the load may be doubled. If you transfer data from an encrypted disk image on an encrypted partition to another such image on another encrypted partition, the load may be quadrupled.

    This issue probably doesn't affect late-model Macs with an Intel i-series, recent Xeon, or later processor. Those processors support hardware-accelerated encryption. You can determine what kind of processor you have by selecting About This Mac from the Apple menu in the menu bar.

    Installed software

    User-installed software that includes a device driver or other kernel code may thrash the kernel. Some system-monitoring applications, such as "iStat," can also contribute to the problem. You can test for this possibility by completely disabling or removing the software according to the developer's instructions, or booting in safe mode (with the shift key held down at the startup chime.) Note, however, that disabling a system modification without removing it or booting in safe mode may not be as easy as you think it is.

    Corrupt NVRAM or SMC data

    In some cases the condition has reportedly been cleared up by resetting the NVRAM or the SMC. I can't confirm.

  • leroydouglas Level 6 Level 6 (13,335 points)

    4SNS/1 40000001 : VPOR-3.839


    Seems to be a System Sensor for Voltage on the Power bus

  • Linc Davis Level 10 Level 10 (107,825 points)

    That's a faulty sensor on the logic board. The board has to be replaced.


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