Lincoln LS Po305 Diagnostic code

Answer 1

That is a misfire code. It means cylinder no. 5 (front driver's side cylinder) is misfiring. These cars have chronic issues with the seals on the valve cover leajing at the interface between the valve covers and the cylinder head where the spark plug journals are located. Each plug has its own coil and what happens is the journal fills with oil and shorts the coil. Take the cap off the valve cover and pull the coil for the no. 5 cylinder. If the boot to the coil is moist at all, this is likely your issue. You can keep replacing the coil every once and a while ($50 each) or you could do it right and replace the valve cover gaskets and seals. Do not drive it if the check engine light is flashing, because that means a cylinder is not firing at all and the unburnt fuel will turn your catalytic converters into little infernos, destroying them and creating a fire hazard. Also, don't skimp on the plugs-anythign less than double platinum will cause high enough resistence to send a false misfire code. Note that this could be your issue too, if the boot is dry. Replace the plugs if you're otherwise due, paying attention to the condition of each.