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iMac OS X wifi issues finally solved

Apple LogoI had been facing brutally slow Internet speeds lately on my iMac. It’s a 27 inch 2009 iMac9,1 model, but a quick search shows many people are having wifi issues with a range of iMacs made in this time frame. The first year was alright, but then slowly I began losing connectivity and getting degrading speeds followed by exceptionally high ping speeds and major packet loss. The tipping point forcing me into all out research mode to find a fix for this issue was when Star Craft 2 starting lagging. I mean I can handle slow downloads, but slowing down while conquering the Zerg? That’s where I draw the line.

Who’s to blame? Not the ISP or router

At first I wanted to blame my ISP, I mean who doesn’t want to blame everything on their ISP? I also suspected my D-Link router. So the first thing I did was run some ping tests on yahoo.com. Here are some of the results before the fix.

64 bytes from icmp_seq=2 ttl=54 time=1116.307 ms
Request timeout for icmp_seq 4
64 bytes from icmp_seq=3 ttl=54 time=2354.040 ms
Request timeout for icmp_seq 6
64 bytes from icmp_seq=4 ttl=54 time=3893.753 ms
Request timeout for icmp_seq 8
64 bytes from icmp_seq=5 ttl=54 time=4051.168 ms
64 bytes from icmp_seq=6 ttl=54 time=3721.117 ms
64 bytes from icmp_seq=7 ttl=54 time=3522.018 ms
64 bytes from icmp_seq=8 ttl=54 time=3532.999 ms
64 bytes from icmp_seq=9 ttl=54 time=2989.983 ms
64 bytes from icmp_seq=10 ttl=54 time=2246.754 ms
64 bytes from icmp_seq=12 ttl=54 time=659.947 ms
64 bytes from icmp_seq=13 ttl=54 time=374.582 ms
64 bytes from icmp_seq=14 ttl=54 time=704.893 ms

As you can see, absolutely abysmal with some requests timing out all together and a packet loss of up to 40% at times. Next I ran the same test on my windows laptop and it came up with normal results, so that basically ruled out the ISP and the Router being at fault; it was Google time.

After reading through several forum threads dealing with this issue I found some options. The first one was to reset PRAM which some people claimed fixed their wifi issues so that’s why I am including it here even though it did not fix my issues. You could even try a Megapath T1 line to see if this helps your problem.

Turn your Mac off and then back on and hit the Command-Option-P-R keys before the grey screen appears. You continue holding these keys until the computer restarts again. What is PRAM you ask? Here’s a snippet from the Apple support site.

A small amount of your computer’s memory, called “parameter random-access memory” or PRAM, stores certain settings in a location that Mac OS X can access quickly. The particular settings that are stored depend on your type of Mac and the types of devices connected to it. The settings include your designated startup disk, display resolution, speaker volume, and other information.

The solution that worked

  1. Go to the Apple icon in the top left corner, click About This Mac, and then click More Info…
  2. Look for Network and then click AirPort below it. This will take a second as your Mac loads all the wifi networks available.
  3. Find your network and look for your Channel number.
  4. Look through the other networks and see what channel they are on. If you see a lot of other networks using the same channel as your router then this may be your problem. Look for a channel number in the range of 1 to 11 not being used, or the number used least.
  5. Log into your router.
  6. Go to your wifi settings, this will vary for all routers, but on my D-Link it was under manual wireless wifi setup. Change the wireless channel to the channel you chose in step 4 and turn off Auto Channel Scan if that is a setting on your router.

That’s it, connect to your wifi network and if things worked it should be much faster. If it did not work try another channel and the reset method mentioned earlier in this article if you haven’t already. If neither of these methods work you might have a bigger problem and may need to send or take your Mac into Apple. You could also pick up a wireless adapter which was going to be my next step, since lugging my iMac into an Apple store didn’t seem like much fun.

The Results

It’s a night and day difference now and downloads are at least 10 times faster, and I’m doing better in Star Craft 2 already. Here were my ping results after this tune up with zero packet loss.

64 bytes from icmp_seq=0 ttl=55 time=24.496 ms
64 bytes from icmp_seq=1 ttl=55 time=37.596 ms
64 bytes from icmp_seq=2 ttl=55 time=30.118 ms
64 bytes from icmp_seq=3 ttl=55 time=27.434 ms
64 bytes from icmp_seq=4 ttl=55 time=45.736 ms
64 bytes from icmp_seq=5 ttl=55 time=28.150 ms
64 bytes from icmp_seq=6 ttl=55 time=30.143 ms
64 bytes from icmp_seq=7 ttl=55 time=24.516 ms
64 bytes from icmp_seq=8 ttl=55 time=38.174 ms
64 bytes from icmp_seq=9 ttl=55 time=32.034 ms
64 bytes from icmp_seq=10 ttl=55 time=29.954 ms
64 bytes from icmp_seq=11 ttl=55 time=42.683 ms
64 bytes from icmp_seq=12 ttl=55 time=28.703 ms
64 bytes from icmp_seq=13 ttl=55 time=64.164 ms

Although for now the problem is solved, this is still an Apple issue as far as I am concerned, sure it’s nice that I was able to work around it, but it shouldn’t be an issue. I have 3 other laptops in my apartment that worked just fine with the router on the previous channel. I hope this fix is permanent, although I may need to change it again in the future. For now all is well and I hope this works for anyone else having these issues. If you are still stumped you can also check out the original forum thread.

44 Comments to “iMac OS X wifi issues finally solved”

  • Jim

    Thanks for this. I too have a 2009 27″ iMac that has similar WiFi issues. No problems with my Win PC’s, or i-Touch. The Apple store could not fix it, so they gave me a replacement unit, but it’s experiencing the same behavior.


    • Ian Hoar

      It’s definitely something wonky with the iMac network cards, but changing the channel is also a good idea. A lot of routers ship with a default of channel 6. In my building there were a lot of channel 6 signals and that can cause interference.

      Since I wrote this article I have since changed my channel again. Unfortunately there are a lot of wireless networks around me and that’s probably wreaking havoc with the iMacs network card.

      • Emil Valsson

        I’m having the same issue with my new 27″ iMac i7, but I’m using the wired connection, not the wifi. Resetting the PRAM/SMC does not help. 🙁

      • Ian Hoar

        If you are having wired problems I might get it looked at. Have you checked if the wifi works? My issue is still intermittent sometimes.

    • Henk

      Turn off IPv6 in WiFi by going to

      System Preferences>Network>WiFi>Advanced>TCP/IP>Configure IPv6

      and change “Automatic” to “OFF”.

      Safari has problems with IPv6 and causes delays, spinning beach ball, WiFi disconnect, and sleep mode problems if set to automatic.

  • Mike Lawson

    I’m having problems with my wired connection, after upgrading to Snow Leopard. Connections to addresses within the local subnet will become unreachable, then magically reappear. Since this is all by IP address, DNS shouldn’t have much to do with it. Since the traffic is to adjacent IP addresses, routing shouldn’t have anything to do with it, either. I can be connected via SSH to an adjacent address, and it will just hang, after some random length of time. I fire up another terminal and ping that IP. No joy. Traceroute it. No joy. Just lots of lines with ***. Try another local address, and everything is fine. A few minutes later, the first address starts working again. Ping works. Traceroute shows no intermediate hops, or ***s. This never happened when I was on Leopard, and before our admins started playing with IPv6. It happened on occasion, while on Leopard, when they started playing with IPv6. After upgrading to Snow Leopard, it happens constantly. I just turn off the wired connection, and all is well via the wireless. Also, there’s no IPv6 on that network. I should also say that the wired connection was configured manually, with a static IP, and IPv6 explicitly turned off. I’m about to give up and install Leopard again, from scratch, without importing anything from an old image, just to be sure, on the remote chance that something odd, from some ancient config, carried over from 10 years ago, might be confusing the system.

  • Emil Valsson

    This looks to be OSX issue, I had my i7 replaced and this is still happening. When I encounter this issue (browsing halts on Safari due to packetloss) I goto my Internet Explorer in my Windows 7 Parallels setup and I can browse there. 🙂

    • Ian Hoar

      I find sometimes starting and stopping airport helps. This really shouldn’t be happening on iMacs at all. My wifi has been pretty good since I switched the channel number. It got reset a few weeks ago and slow right down again.

  • Emil Valsson

    Well, after googling much about the issue I found a solution I think. Lowering the MTU for the ethernet from 1500 to 1458 seems to have solved this issue. At least I haven’t experienced packetloss since yesterday. 🙂

  • Emil Valsson

    I was too quick, it’s started again, god I hate this problem.

  • Susan

    I have also had this problem on a 20″ 2007 IMac. At first, the wireless just used to not come back after sleep, but then it stopped being able to hold a signal (for different lengths of time – no pattern found), especially if I had the ethernet plugged in too. It is almost as if it doesn’t continuously scan to maintain its contact.

    If I restart or turn airport off and on, it comes back without a problem. If it drops and I click on airport, it scans and sometimes comes back right away, other times it takes a while (you have to keep the airport drop down open though or it stops).

    The interesting thing is that this doesn’t happen under boocamp with XP. I maintain continuous wireless there, so it can’t be the hardware.

    I have spent hours with Apple resetting configuration, etc. and nothing works. I think there is a glitch in 10.5.8. I have a macbook with the same OS, and powerbooks, and none of them have an issue with wireless at all. No drops. Only this IMac which sits about 5 feet away from the router (have tried laptops up that close, and no problem with them).

    I do not have any 2.4 phones. Again, if there was also a problem on the XP side, I would think there was an external or hardware conflict, but it is only on the Mac side.

    I don’t want to archive and install if I don’t have to since many who have done so have not had positive results. Any thoughts most appreciated.

    • Ian Hoar

      That’s really interesting that it works fine under boot camp. I find turning on and off my airport also helps, but every now and then I check the channels being used in my building via my router admin. I always make sure I am using the channel least used. I find over time my connection still deteriorates, but a quick disable/enable of the airport seems to fix this problem.

      It’s good to know that this may be a software issue and not a hardware issue, but still annoying none the less.

  • Susan

    One more comment – I have also hooked into my neighbor’s wireless (with permission), and have the same problems, so that also rules out my router. She has a different brand and ISP.

  • Alberto

    it doesn’t work for me.

    try this instead: http://discussions.apple.com/message.jspa?messageID=12914636
    read tenortim’s post. hope this works!

    1) Download the 10.6.4 Combo update and the Pacifist program that allows one to extract files from, amongst others, “.pkg” files.
    2) Mount the update .dmg, open the package in pacifist, extract the subtree “/System/Library/Extensions/IO80211Family.kext” to a convenient location.
    3) As root, cd to /System/Library/Extensions, rename IO80211Family.kext to IO8021Family.10_6_6 (or anything else to back it up), and copy in the replacement IO80211Family.kext that we extracted from 10.6.4.
    4) Download, install and run “Kext Utility” (Google it, it’s at Insanely Mac). It should ask for your password, run, and fix up the kext permissions and caches.
    5) Reboot. You should now be on the new (old) driver/firmware. Verify by running “About this Mac” -> “More Info” -> “Network” -> “Airport”. As stated, the newer firmware is, the working firmware is

  • Steve

    Thank you so much for this fix!! I have been off and on trying to remedy my slow internet connection for about 3 years, and I must have called both Apple and Comcast 20 or 30 times since. No one told me about switching the channels! I live in a congested city and normally have anywhere from 15-20 other networks in range of my computer. I looked through the index of channels and found 7 other networks on the same channel as mine! Keeping my fingers crossed my internet doesn’t gradually slow to a complete stop as it usually does before I must restart the computer, but so far so good. BTW, I had a 27″ imac from around 2009, but it was a lemon, and after 4 major fixes, they finally gave me another. The second’s harddrive failed in 3 days, Apple noted that they may have given me a faulty computer (AGAIN!!), so I’m on my third. Lot of finger crossing going on here! Personally, I feel we should need more than hope and prayer to get our computers to function properly. Why does it seem Apple isn’t making computers like they used to (rather, this is more of what I experienced with my first few–non-Apple–computers)!

    • Ian Hoar

      Hey Steve, hope it helps, I find anything involving wifi hit and miss. It’s hard to pin point the blame too, sometimes it’s the router and sometimes it’s the computer. My iPhone used to connect to my wifi fine, but now I can never get it to connect, my iPad on the other hand has no problems connecting. The iMac has worked fairly well, but now and then I find the channel changes and I have to go back and fiddle with it. A reboot of the router from time to time helps too I find.

  • Cherise

    Hi Ian,

    I just bought a new iMac 3,1 GHz Intel Core i5 yesterday and discovered the Wi-Fi problems. Is your solution still relevant and do you think it would work on this particular iMac?

    I am just cautious and obviously don’t want to mess up something…

    Do I have to do the “Cmd+Option+P+R” step first before changing the channel?


    • Ian Hoar

      Hi Cherise,

      The Cmd+Option+P+R is one solution that has worked for some, the router channel change is another. You can try both to see which works for you. The one that worked for me was changing the channel on my router. This is usually an issue if you live in a building or a place with lots of wifi signals.

      I should add that I’ve had to update the channel on a regular basis and I find my iMac in general has poor wifi compared to other devices, but in fairness I’m using my Mac a lot more than the other devices, so maybe they have the same issues. It’s really hard to know if it’s the router or Mac that is causing the problem.

      • Cherise

        Hi Ian,

        I’m a little uncertain about the first option, so I guess I’ll try changing the channel first. I use my iPhone and iPad a lot and so does my husband. I also have a MacBook which has been working beautifully for almost a year now. It’s just the iMac giving problems.

        It’s very frustrating. I literally sit and watch the connection drop every 4 minutes or so. We live in a residential estate in South Africa, and there are a few other wi-fi signals which I pick up. Checking up on the “this mac” info, one other user is using the same channel (11).

        Just one more question: Do I only need to change the channel on the router, or on the iMac as well?

        On your steps (1-4) it indicates going into “This Mac” but if I do that, it doesn’t allow me to change anything even though I can see the channel there.

        Forgive my ignorance 🙂

  • Cherise

    Hi Ian,

    I changed the channel to 3 now…(didn’t read your instructions properly the first time).

    Hoping this works…


  • Osnath

    Thank u so much!
    I’ve been tying for a month now and couldn’t find a solution.
    Now I can finally use Internet in a normal speed!

  • Lucas

    Really thank you for your suggestion about changing channel number in the router. It works for my iMac 21 inch 2011! Really appreciate it! In the past , I could not use my iMac wirelessly more than 10mn , it disconnects without reason.Now with your solution, everything is good, I am really really happy! Thanks!

  • christina

    Thanks! this worked for me so far!

  • Dessimat0r

    Just a note from a network engineer — don’t screw with the MTU. Lots of apps depend on the value being 1500.

  • Jonas

    Thank you – I knew I read it somewhere – but your post really sums it up.
    I hope this help will climb up the google search ladder 😀

    Thank you for sharing!

  • Conny

    My problem is about 50% slower wifi speed in macos than bootcamp/win7

    Tried several diffrent solution no go, and if it works in bootcamp/windows 7 that means its not hardware related to me.

    Only thing i havent tried is reinstalling macos but atm i dont have the time.

    My comp is, imac i5 27″ mid 2011

    • Ian Hoar

      Really interesting to hear that it may just be a software issue. I haven’t had any issues lately, but sometimes they will randomly pop up again. Changing my router channel has worked well though.

  • Daniel

    It’s incredible the amount of people with this issue, world wide. My iMac has gone nuts too. I saw a small difference when switching the channel in the router, i also see differences when you restart the machine and come back fresh, but all of these will only work for a very short period of time. I’de less than an hour or so. Will do the cmd+p r keys in the boot, see if i get any where. I also tried some DNS configs, and some automatic pinging on yahoo servers, lol, and that was because wifi just kept dropping so i had to keep it downloading something etc.. Also have to mention that there was an update, recent, February 2012 if i’m not mistaken, that sorted out some problems with Wifi in Lion.

  • Yigit

    Solved my problem. Thanks.

  • Phil

    I have a suddenly slow Airport wifi on my late 2009 iMac. Turning it off and on again sometimes works but I’d like to try changing the channel in my router – but I don’t know where to access it and “log in” to do the change. Any help would be great!

    • Ian Hoar

      Hi Phil,

      It really depends on your router as each router has different software. Usually you will log into it via your browser. You need to log into the admin and then dig around and find where the channels are set.

  • Gloria

    We were having problems with an iMac 27″ and they got much worse when we installed Mountain Lion. Trying to contact Apple has been useless. I will try the suggestions above. Our laptops have no problems with wifi.


  • Laurel

    I have a 27″ imac w/ Lion as well… when I first got it, I had major issues with wifi, but calling Apple was unhelpful; I figured that I had problems because I was in a large apartment complex with shared wifi. When I moved, the problem went away and I never had issues. I just moved again, and we set up a new wireless router, and suddenly it’s going crazy again. It says that I have full wireless power (which makes sense; the router is in the room next to me), but the net goes out constantly. I have to turn it on and off again over and over.

    On my iMac, I can’t figure out how to choose a different channel like your solution here. The menus don’t have the same options. Do you have a solution for iMac? Thanks!


  • DPJ

    Same problem, solved it perfectly, thank you!!!!

  • Kyle

    This totally worked for me! Was getting download rates of 15 mbps on my iPhone, but 1 mpbs on my iMac (21.5″ 2009) on the same network. I looked and about 50% of surrounding networks were using channel 1, along with myself.

    I found the one channel that no one was using and now i am getting 15mbps on my imac too!

    You are a life saver!!

  • Johannes

    Ian, thank you so much! You really saved my day. Much appreciated!


  • Chris

    Clearing PRAM worked for me! THANK YOU!

  • Andy

    This has also worked for me. I has done this previously but had forgotten all about it, I just moved and my new ISP provided a new modem/router and my wireless had gotten painfully slow. All sorted now thanks.

    Another interesting side effect that I have had, My screen was beginning to flicker or sometimes go dull at top 1/3. I figured it was the backlight dropping out and have been looking for a replacement bulb. However, after clearing the PRAM, problem solved. Weird!

  • Zak

    Ian, I owe you a f***ing beer – problem solved 😀

  • Tim Cassidy

    Hi Ian,

    Thanks a mil you are a lifesaver 😀 got a brand new iMac have had this problem from the get-go, sent Apple an email with this link, thought it might help a lot of people with the same problem.


  • Mary

    I want to know why my network is unlocked at startup ?