Many iPhone 3G users who have switched to iOS 4 have noticed significant slowdowns in their devices. The solution to these problems was the return to firmware 3.1.3. The process itself is quite simple.
Necessary
Firmware image 3.1.3. RecBoot utility
Instructions
Step 1
Make sure the backup firmware version 3.1.3 is saved on your computer. It should be located in - / Library / iTunes / iPhone Software Updates (for Mac OS) or C: / Documents and Settings / username / Application Data / Apple Computer / iTunes / iPhone Software Updates (for Windows OS).
The firmware image may look like: iPhone1, _3.1.3_7E18_Restore.ipsw or iPhone1, 2_3.1.3_7E18_Restore.ipsw.
If no backup is available, use the list of iPhone compatible firmware files on the iClarified website to download the correct version.
Step 2
Download the RecBoot utility (Mac OS and Windows OS versions available).
Step 3
Connect iPhone to computer to enter DFU mode.
Step 4
Turn off the device by holding the power button at the top of the device until the shutdown warning appears.
Step 5
Press the On / Off button of the device and the Home button at the same time. Keep them pressed for 10 seconds.
Step 6
Release the On / Off button of the device while continuing to hold the Home button.
Step 7
Wait for the message that iTunes has detected the device in recovery mode and a black screen appears.
Step 8
Select your device in the Devices list in iTunes on your computer and hold down Shift (for Windows OS) or Alt / Opt + Click (for Mac OS) and click the Restore button.
Step 9
Specify the firmware backup in the iTunes pop-up window. The recovery process can take up to 10 minutes.
Step 10
Wait for a warning message from the iTunes application about the impossibility of recovery and start to boot the device with a proposal to connect to iTunes on the screen.
Step 11
Open the RecBoot program and select Exit Recovery Mode. This will start booting from the saved copy of firmware version 3.1.3.
Step 12
Sync backed up data and apps to restore your information to iPhone.
