I installed iOS 4 on my iPhone 3G and now I hate it. It’s really slow and the screen often acts like it’s numb. Plus, it takes forever for it to respond. Is there any way I can uninstall iOS 4 and go back to what I had?
Note that Apple’s iOS 4.1 update is supposed to solve some of the problems of iOS 4. Before I offer instructions for downgrading, switch off your phone and start it again. Sometimes this can clear out the cruft that’s slowing down your phone. If that doesn’t work, try restoring your phone again with iOS 4. That second restore may set things right. If no joy, read on.
Lifehacker has put together a useful article on this subject – see www.macworld.com/6392. In the meantime, here’s the gist for downgrading the iPhone 3G (not the 3GS). Locate or download a copy of the iPhone OS 3.1.3 .ipsw file (Lifehacker points to some sources). Put your phone into Device Firmware Update (DFU) mode by plugging in the phone, turning off the power, pressing and holding the Sleep/Wake and Home buttons simultaneously for 10 seconds, and then letting go of the Sleep/Wake button but continuing to hold the Home button for 10 more seconds. iTunes will then throw up an error message telling you that the phone is in recovery mode.
Select the iPhone in iTunes’ Source list. Hold down the Option key and click Restore. You’ll be prompted to choose a file to update from. Navigate to the 3.1.3 .ipsw file and click Choose. You’ll likely see an error message on your Mac, and the phone will ask that you connect to iTunes. Download a free copy of RecBoot (www.sebby.net). In the RecBoot package you’ll find the RecBoot Exit Only application. Launch it and use it to compel your iPhone to leave recovery mode.
Your iPhone should now boot to the Home screen. Restore it from a backup in iTunes. At this point it should be running the iPhone OS 3.1.3 software.