My 99 ford expedition 5.4L is miss firing. I have done my research and understand the process in changing the spark plugs. I don't believe that it is the coil packs because my service engine light has not come on and there are no codes thrown. I have been warned that I can brake the plugs off and would need an extraction tool to remove them, is this true? Or is it that its more problematic to strip the aluminum heads by over tighting them or cross threading them. Thank you for your help.
You do not have the 3 valve engine that breaks off the spark plugs. The only issue yours has with spark plug threads is that they tend to loosen up and blow out after ruining the threads if they are not torqued correctly. You should have any problem getting them out but let me tell you, this job is no picnic on that truck and don't assume your coils are good. You probably have a couple weak ones and you really need to determine which ones they are. They don't always set codes because they are inconsistent. You may be able to see raw misfire counts with a professional scan tool. You definitely should replace the coils on the cylinders that are misfiring once you diagnose them.