Q: Gas smell while driving.

Smelling a gas odor coming from your vehicle is never good experience and it usually means there is a leak somewhere. From the description provided, it is quite possible that the EVAP Purge Canister has developed a leak and needs to be replaced on your vehicle. This canister captures gas fumes from entering the atmosphere and occasionally will need to replaced.

Other common situations I have seen concerning the vehicle and gas smells are when o-rings and seals, found on the fuel rail, go bad. They will develop a small but big enough leak to emit a gas odor, though your car may not actually be leaking gas. Another situation that comes to mind concerning the gas smell is when the back spark plugs were not torqued correctly after being replaced and then come loose, allowing once again a gas odor to escape the combustion chamber.

It was mentioned that five of your Expedition’s spark plugs were replaced and one was covered in oil. Spark plugs need to all be replaced at the same time in order for the engine to run efficiently and it is recommended this always be done. The spark plugs need to be torqued down to factory specifications as well so it is important that this is verified. In regards to the plug with oil on it, I would assume the vehicle may have developed a leak in the spark plug tube which allows oil to enter the orifice. With concerns like these, I would highly recommend enlisting the help of a certified mechanic as soon as possible to inspect your problems and avoid issues advancing in the future.