Macbook model A1342 randomly freezing

hangmacbook pro

I have a Macbook white model A1342 that I'm fixing for a friend of mine.

The macbook will freeze up totally randomly (usually while surfing the net but it happened even when no browser was opened). Freezes are usually 2-3 per day, but once it starts freezing it will freeze again in due time
It freezes without any beach ball spinning up, the cursor remains where it is and the only solution is shutting it down via the power button.
When I took it from my friend for fixing, it had only 2gb of ram and mavericks installed, and was painfully slow. I thought that was the culprit and installed 4gb of RAM, but it freezed again, today, just after installing the RAM, like nothing changed.
AHT and memtest won't report any errors, and the system log reports warning like disk swapping but nothing too dramatic. Tried etrecheck too, apple support's app for checking your system and nothing wrong reported here too.
Here is a list of what I tried so far:

  1. upgraded to 4gb of RAM
  2. clean reinstall of mac os lion
  3. tried swapping disk, Mac freezes the same.
  4. opened up the bottom lid and checked if fan is on, it seems to be
    working ok.

I should add that the macbook has an erratic airport card. It often won't get detected by the system. Could a faulty airport card be the culprit of these freezes?

I'm pasting what the system.log reported just before this morning's crash (I don't know if it helps):

Apr 29 12:30:44 macbook-di-luca iBackup[376]: "download and install new plugins"
Apr 29 12:30:54 macbook-di-luca mdworker[327]: (Error) Import: Couldn't recover plist from xattr com.apple.metadata:kMDLabel_xjx7qauyg5mltgjdmyyeartz4e     
Apr 29 12:31:41: --- last message repeated 5 times ---  
Apr 29 12:33:16 macbook-di-luca KernelEventAgent[43]: tid 00000000 received event(s) VQ_LOWDISK, VQ_VERYLOWDISK (516)   
Apr 29 12:33:17 macbook-di-luca Finder[125]: _GetISImageRefFromIconRefInternal: could not retain image ref 0x213c0055 (err=-2580)
Apr 29 12:33:17: --- last message repeated 1 time ---   
Apr 29 12:33:17 macbook-di-luca UserEventAgent[11]: Cleaning up local snapshots on volume file://localhost/Volumes/WD-GIGI/ 
Apr 29 12:33:20 macbook-di-luca Finder[125]: ISGetIconFamilyFromStorage: seed mismatch for 22c20010, actual seed is 109cf92e    
Apr 29 12:33:20 macbook-di-luca Finder[125]: ISGetIconFamilyFromStorage: seed mismatch for 213c0055, actual seed is 39386575    
Apr 29 12:33:22: --- last message repeated 1 time ---
Apr 29 12:33:22 macbook-di-luca xpchelper[481]: for uid: 501 -- timeout while waiting on FSEvents flush; clearing cache.

After that it freezed up for good like usual, without any warning.
Thanks a lot for any suggestion and help in advance. I'm quite discouraged and can't seem to find the solution to the problem, and I don't want to start swapping parts randomly.

Best Answer

I have a suggestion to avoid "swapping parts randomly".

Start by disconnecting all unnecessary parts from the logic board to make a "minimal machine". For example: disconnect optical drive, airport/bluetooth card, speaker (this might seem odd, but I have occasionally found faulty speakers to be the cause of issues which don't seem at all related to sound), battery, leave only one RAM chip installed.

Test the machine for a day using this minimal machine.

If you see a freeze, unfortunately the issue relates to one of the components that remain. In that situation, try to make the machine even more minimal. (The ultimate here is logic board, RAM, power input, power button and speaker... if this setup doesn't give the startup chime, one of those components is faulty... unfortunately this won't help with your intermittent freezing, but I mention it to try and illustrate the minimal machine idea a bit more.)

If you don't see a freeze, probably the issue is caused by one of the components you disconnected. Try adding one at a time, repeating the day-long test each time, to narrow down which is the cause.

An erratic airport card certainly could be the cause of intermittent freezes. Before you try the minimal machine idea (which can take some time), I think it's certainly worth testing the machine for a day with that card disconnected.