Why is my ADSL Sync rate low

4 If your sync rates are low or poor this indicates that there is a physical line issue. The troubleshooting for this is quite simple and can generally be done in one         sitting.

1. Power cycle the modem 
2. Isolate the line - Remove every device that plugs into any phone socket, by doing this it removes any chance of incorrectly filtered / damaged devices causing interference.
3. Try with a different phone cable - This is to test if the phone cable connecting the modem to the wall socket is damaged.
4. Try at a different phone socket - To rule out any possible internal wiring issues.
5. Factory reset the modem - Only do so if it is possible to reconfigure the service easily. Do not do this if the customer has any custom settings etc. VoIP Wireless port forwarding etc, this is to make sure the modem hasn't locked up
6. Test the modem at another location or try with a different modem
7. Troubleshooting throughput issues. 
8. Use/Replace ADSL Filter.