Cylinder #8 missfiring with pil on the spark plug

Hello, Dave here, contributing to RepairPal and providing expert advice since 2010. How many miles are on this 4.6L V8 engine equipped with your Town Car? If changing the plug and coil is no help, and you have oil on the spark plug coming out - it could be there is a compression concern in cylinder number 8. Check engine compression pressure in all 8 cylinders. If #8 (and others) are significantly lower than the rest, there is an internal engine issue that requires repairing. You can do a cylinder leak down test after if this is the case, to determine if you have a valve or cylinder issue. Certainly there could be other things causing a cylinder 8 misfire, but based on the information you shared in your question, this is where I would start. You can always obtain assistance from a shop near you -- https://repairpal.com/auto-repair-near-me Click the link or call us at 877-913-1554. We'll gladly find you a certified RepairPal shop in your area.