Engine light solid slight misfire 3 cylinder

3 plugs in front 3 along firewall.06 Buick allure CSX 3.6l.we have done that with oil but what is chance it will get in.damn aluminum heads lol.I am going to try to have them loosen in day or so but thank u.will keep u posted.he was able to get 1 plug out left front.hoping this will work.car still runs good they erased code and have driven for day or so but I know it takes a few times starting for code to register.

Thank u.will have them try.oil went on their already if deisal is put on only once will they come out if we let them sit for hour.? Mechanic also suggested after he sprayed with oil to come in in few days.will pass along info