MacBook Pro acting weird at startup

Question

Hi,
First of all thank you for reading this, it's quite a long story. And sorry for any grammatical mistakes, I'm Dutch.
Summary
My MBP suddenly has been acting really weird: kernel_task eating 150-200% of the CPU which caused a super slow MBP, power button not working well, and MBP shutdown after ten minutes without touching it and with the battery on 90%. I did a clean install of OS X Lion, some PRAM and SMC resets and removed the MacBookPro7_1.plist file from the system library. The kernel_task high CPU problem is now fixed. But the power button is still not working: most of the time my MBP shuts down three seconds after I push the power button in a first attempt. In the second attempt I hold it for like five seconds and this works. Sometimes it works fine on the first attempt. Restarting the MBP from the desktop works fine. I'm also worried about the random shutdown. What could probably cause the problem with the power button and the MBP shutting down when I don't touch it, and is there a way to fix this myself? I'm not really into tech, so please keep your answer simple.
My MacBook Pro "13 (mid 2010) with OS X Lion has always been a charm since I bought it. I've never had any problems with my MBP until now. Two weeks ago I was going on a holiday and had to check a few things on my MBP in a hurry right before I was leaving. I'm afraid I forgot to turn off my MBP before I went on my holiday, but I can't remember this exactly. When I came back after a week, my MBP started acting weird at startup and then became really slow. The kernel_task was eating my CPU with 200% and I've tried many things to fix the MBP myself but it still isn't working well. I hope you can help me with this.
This is what happened:
1. When I push the power button to start my MBP, the first time it shuts down three seconds after I push the button. After the first attempt I hold the power button for five seconds, and my MBP turns on the right way. After all the fixes I've done this is still an issue.
2. When I finally got my MBP started the first time after my holiday, it was really really really slow. I later found out that the cause was the kernel_task eating my CPU. It was using 150-200% with no applications running.
3. The MBP was acting normally (not slow) in safe mode, but in safe mode I couldn't open some sites in Google Chrome, like Facebook and Google Maps. So this didn't work either (and was not the solution to my problem).
4. I did some things with PRAM and SMC reset but this didn't work.
5. A clean install was already on my mind for weeks, so I decided that this was the right moment. After I did a manual backup (not with Time Machine) I restarted my MBP holding some buttons to startup the OS X Utilities screen. I first erased my Macintosh HD and then I wanted to install Mavericks because that was the only option from the menu. It took me five hours and at the end it came up with a 'can't download Mavericks, try again' screen. The MBP wasn't starting up anymore because OS X Lion was already erased.
6. So I became annoyed and decided to use my original Snow Leopard dvd which came with my MBP. Installing Snow Leopard took me two days!!!!!!!
7. When I finally got Snow Leopard installed, it still was really really slow and the kernel_task was messing up my CPU again.
8. After some hours of searching on the internet, I read the following thing: fixing the kernel_task problem was easy by removing a file from the system library (http://www.rdoxenham.com/?p=259). Of course I've researched this solution because I'm not a fan of changing things in the system. But I decided to give this a try and it worked! Like a charm!
9. I still was on Snow Leopard and decided to upgrade to Lion again, because I did know for sure that my MBP could handle Lion and I wasn't sure with Mavericks. So I first downloaded Lion from the App Store and then opened the installation program. This took me one day again, probably because the file from the system library was put back with the installation of Lion...
10. When I finally got Lion running, the kernel_task was using a high CPU% again so I removed the file from the system library again and restarted my MBP. This worked.
11. I'm working on Lion for a day now and I've installed some applications (Adobe CS5 Master Collection, Office for Mac, updated my 17.000 mails in Mac Mail, and installed some browsers). It's working fine and the kernel_task is at 1-10%. The issue with the power button is still there but sometimes it works fine at the first attempt. Yesterday my MBP suddenly shut down when I didn't touch it for like ten minutes. The battery was still on 90%. Maybe this was caused by the fact that my MBP was running for four days non stop because of the OS X installations, and it was a hot day yesterday.
So this is what I've done so far in this order:
1. First of all I did a manual backup on my external HDD. Not with Time Machine.
2. I tried to restart my MBP multiple times. Restarting from the desktop worked well, but shutting it down and than turning it on with the power button didn't work well.
3. I did PRAM and SMC resets multiple times.
4. I decided to do a clean install and erased my Macintosh HD from the OS X Utilities screen at startup.
5. Then I wanted to upgrade from Lion to Mavericks but Mavericks couldn't be downloaded.
6. I've installed Snow Leopard from the original dvd, this took me two days.
7. I've followed the instructions from http://www.rdoxenham.com/?p=259 (remove the file MacBookPro7_1.plist from the system library) and this worked for my MBP.
8. Because my MBP was working fine again, I decided to upgrade to Lion. This took me one day.
9. My MBP was really slow again: Lion put the MacBookPro7_1.plist back in the system library so I removed it again. This worked.
10. The problem with the power button still holds so I did a SMC reset again. Didn't work. My MBP also shut down yesterday when I didn't touch it for like ten minutes. I hope this was caused by the fact that the MBP was running for four days non stop, and it was a hot day so maybe it was overheated.
So everything is working fine again, but the power button still isn't. Most of the time my MBP shuts down three seconds after I push the power button. In the second attempt I hold it for like five seconds and this works. Restarting the MBP from the desktop works fine, and the kernel_task is now using 1-10%. I'm also worried about my MBP suddenly shutting down. Is there a way to fix this myself?
Thank you!
Regards,
TokkieTor

Answer 1

TokkieTor,
This is the full error message I got from the test:
4SNS/1/40000000: IP0R-9:166
I read that those letters (IP0R) stand for different errors in the hardware, in my case it's something with the Power Bus according to this website: http://www.cnet.com/news/how-to-invoke-and-interpret-the-apple-hardware-tests/.
Again, I'm really not into tech so what is a Power Bus and should I be worried?
what you have is a problem with a sensor which monitors power bus current. The power bus is the main pathway along which electricity travels in your MacBook Pro. If the sensor isn’t individually repairable, then you could have reason to worry — if they tell you that a logic board replacement would be needed, then that could cost hundreds of euros. (One would hope that replacing a sensor would not require a logic board replacement, but only hardware experts can say for sure.)
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