There is a way to clean it
Take the phone's logicboard out, and put it in 97% isapropyl alcohol, and scrub it with a toothbrush gently, but not too hard, just enough to clean it
As to the connectors i the phone, dip the toothbrush in the alcohol and clean those
here is how to remove the logicboard
iPhone 4 Logic Board Replacement
iPhone 4 Dock Connector Replacement
when doing this, don't insert the speakers in the rubbing alcohol
After you do this, replace the battery, this usually shorts, and batteries hate water, so it could blow up, this will be changed for safety reasons in the future
iPhone 4 Battery
iPhone 4 Battery Replacement
After the phone is cleaned and dried, reset the phone by holding the home and power buttons, this is so it can be tested in a stale way
Report back with the results after cleaning it