iPhone 4: Slow Downloads and Data Over 3G; Fixes

Although most users have reported faster 3G data throughput from the iPhone 4 relative to the iPhone 3G and iPhone 3GS, some users report dramatically slower speeds in locations where their previous iPhones delivered normal speed. In some cases, the phone displays the message “Could not activate cellular data network” despite full signal (all bars).

Apple Discussions poster bgrind1 describes a test in which two iPhone 4 units placed side by side both delivered dismal 3G throughput, while an iPhone 3GS in the same location delivered normal speed.

“I just visited an ATT store to ask about this issue. The rep and I tested their two display iPhone4 models and both responded exactly as mine, with little or no 3G data. We simply tried to open yahoo on both display phones as well as mine. All three after 2-3 minutes responded with an error stating no response from server, or something along those lines.

“Meanwhile, the iPhone 3GS model 5 feet away, also connected to 3G, responded very quickly, to all websites, apps that require data, etc.”

Note that this issue is separate from the signal/reception loss issue (see: iPhone 4 Loses Signal [“Death Grip” Antenna Issue]: Why and How to Fix [Scotch Tape]. In this issue, signal and reception remain strong, but data throughput is extremely slow or wildly fluctuates, even though grip is not changed and the phone is in the same location.

Another Apple Discussions poster, USBSlave, writes:

“At some points it works fine but most of the time I can pull down a few KBs a second if I’m lucky preventing me from using Data on the phone. Voice and Texting work fine at all points in time. The phone shows 5 bars and I used an iPhone 3G in the same office for a year without a single issue. While I generally use my phone at the office most the problem happens everywhere so its not just one area. Basically the download speeds will spike to 1-4 MBPS for a minute or less then the rest of the time all the speed apps gauge me at about 1-100 KBPS. Upload speeds are always high its only download.”


Reset network settings. On your iPhone, open Settings, then navigate to “General” in the left-hand pane. Scroll down and tap Reset, then select “Reset Network Settings.” This will delete any stored WiFi passwords and other information, but may result in a faster connection.

Hard reset. Hold down the sleep/wake and home buttons simultaneously for roughly 15-20 seconds, until the screen powers off then an Apple logo appears, which signifies a reboot.

Reseat SIM. Remove your SIM card, clean it lightly using a dry cloth, ensure that there is no debris in the SIM slot, then reinsert the card, ensuring a snug fit. Instructions for doing so can be found in this Apple Knowledge Base article.

Switch to EDGE. Albeit a less-than-ideal solution, several users have experienced faster throughput via EDGE than 3G when this issue manifests.

Feedback? info@appletoolbox.com.


  1. says

    Thank you so much for this info…like everyone else I thought I was going bonkers waiting for the pages to load and AT&T and Apple reps were clueless. Your awesome you are on my bookmark bar for life : ) Oh by the way I did all steps except for the Edge step since it worked beautifully after performing all the resets and cleaning the sim card. Hope this helps someone else ..thanks again !!!

  2. says

    I started having these S-L-O-W 3G issues today. I tried all the methods and the only one that worked was switching over to EDGE. To give you an idea of how bad it is, I used the Speedtest app to test it out. 3G (when the test was able to even run) was downloading between at 18 Kbits/s. EDGE killed at between 117-189 Kbits/s. Ridiculous that I’m basically running at iPhone 2G speeds.

  3. says

    I just went to the AT&T store with my 3G data slowness complaints and they provisioned a new microSIM. Problem solved!

  4. says

    I just received my iPhone 4 from Vodafone Australia. At first my 3G Internet was basically unusable. Websites would take either 5 minutes to load or not load at all. I tried all the above tips with no luck. Even tried 2 new micro sim cards. Vodafone had no idea and wanted to send the phone back to apple.

    I did some research myself and managed to fix the problem. Looks like there is an incompatibility between some networks and iOS 4. The way around this is to change your APN settings. It’s pretty simple, just go to unlockit.co.nz then select your carrier. Do this from your iPhone over wifi.

    Tethering gives some problems now, however I can live without tethering until apple does an update. At least the phone is now usable.

    • says


  5. says

    …”Reset network settings. On your iPhone, open Settings, then navigate to “General” in the left-hand pane. Scroll down and tap Reset, then select “Reset Network Settings.” This will delete any stored WiFi passwords and other information, but may result in a faster connection.”…

    Was the fix for me!!! Thank you! The iStore and cellular provider couldn’t fix, and i even spent hours downgrading from iOS4.2 t

  6. says

    The only fix that worked for me is the “switching to edge” thing… I hate it to think that I bought an iPhone to stay on the edge network. But it is so fast! It’s impossible that it really is edge… I personnaly think think that they inversed the 3g/edge switch in the core coding.

  7. says

    In Honduras apresa are usually 1mb.  Ive been getting 0.4-0.5kb.  I tried resetting, hard reset, edge and sim cleaning to no avail.  It started happening yesterday after 3 months Of having my i4.  Have no idea what to do

    Sent from my i4 :-)

  8. Nestea says

    I recently started experiencing significant slowness after a month of using my iPhone 4. I reset the network settings under general and everything started as fast as it use to.

  9. Clueless N00B says

    Thank you for the information. I was going to do everything on the list, but just resetting the network settings did the trick!

  10. Gus says

    Same for me in brazil (VIVO user). Why apple doesnt care about that? Resets work temporally. the problem gets back…

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