My Macbook Pro is running very slow and "thinking" a lot (getting the spinning pinwheel). The fan is running constantly and the Task_Kernel is using 706% CPU according to the activity monitor. Any ideas?
The kernel is using excessive processor cycles. Below are some possible causes for the condition.
When it gets high temperature readings from the hardware, or a low-voltage reading from the battery, the kernel may try to compensate by interrupting the processor(s) to slow them down and reduce power consumption. This condition can be due to
a buildup of dust on the logic board
high ambient temperature
a worn-out or faulty battery in a portable
the malfunction of a cooling fan or sensor
Note that if the problem is caused by a sensor, there may be no actual overheating or undervoltage.
If the computer is portable, test with and without the AC adapter connected. If kernel_task hogs the processor only on battery power, the fault is in the battery or the logic board. If it happens only on AC power, charging is causing the machine to heat up. That may be normal on some models. CPU usage should drop when charging is complete.
If nothing is wrong with the hardware, then whatever you can do to improve cooling may help.
User-installed software that includes a device driver or other kernel code may thrash the kernel. That category includes virtualization software, such as Parallels and VMware, as well as most commercial "anti-virus" products. 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. 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
Sometimes the problem is cleared up by resetting the NVRAM or the SMC.
Connecting an external LCD display to some MacBook Pro models may cause this issue. If applicable, test by disconnecting the display. You might get better results with a newer LED display.