Most self cleaning ovens contain liners made from a pyrolytic material. Depending on the oven there may be a cycle to run for a few hours which then heats the oven up in an attempt to disintegrate any carbon residue on these liners. Other ovens do not have this function and are designed to self-clean as you cook. Unfortunately self-cleaning liners are good at disintegrating some food substances but really struggle with others. For example they struggle to dislodge roast dinner fat.
We have spoken to a some of the manufacturers regarding the cleaning of self cleaning ovens. If the liners are not self cleaning any longer then they advise that they should be soaked in warm soapy water. If that does not work then they need to be replaced. If the self-cleaning liners are not removable then the oven needs to replaced!
At Oven Ready we place the removable self-cleaning liners in our heated dip tank for cleaning, if that is, they require cleaning. We find this works better than the manufacturers advice of warm soapy water, which we found did very little.