If I have a personal injury lawyer and want to fire him and make a quick settlement, can I do this without talking to my lawyer?

You can fire the attorney and settle the case, but the attorney will still be entitled to his 1/3 fee on the matter, unless he has been on it such a short time that you challenge the issue and show a court that he should only be compensated for the work he has done. In any case however, some of the settlement will go to that attorney