The rubber bot is stuck to the spark plug. You will just have to force them off. If the rubber part comes off and remains on the plug you will have to reach down with somethinglike needle nose pliers to grab the boot and remove it. If it gets damages in the process, it will have to be replace. Use a little dialectic grease (not regular grease) inside when re-installing to avoid this problem.
Sunday, March 15th, 2015 AT 4:11 AM