This 2004 Lincoln town car came in with a rough run condition and codes P0300 and P0304 stored. the standard repair is new spark plugs, new spark plug boot kits and replace #4 coil assembly. I normally do not post tune up type repairs but I decided to do this one to see if there is any interest in this kind of topic. This repair generally applies to any Ford, Lincoln or Mercury with the 4.6 liter engine.
The very first thing that has to be done is to blow off all of the and and dirt from the top of the engine. Once most of it is gone, I take the air inlet tube off of the engine to access the coils and plugs on the driver’s side.
Then I blow more dirt from the top of the engine from where I could not reach before.
There is normally a lot of dirt to blow off and this car was no exception.
To remove the coil assembly, first depress the locking tab on the under side of the connector. Then pull the connector from the coil assembly.
Next a 7 mm headed screw needs to be removed.
Then pull the coil away from the underside of the fuel rail or anything else that may inhibit it’s removal. The Boot will normally be stuck on the spark plug so it may take some pulling and twisting to get it to come free.
This particular coil was removed from cylinder number five. It has an obvious arc mark on the side and should not be reused. I thought it was a little strange that the PCM had a code P0304 stored and not a P0305 stored given the condition of this coil.
The number six coil is on the left and again the one on the right with the obvious arc mark is from cylinder number five. My plan was to now replace coils 4 and 5.
When reusing a coil and new boot kit should be installed. The boot will easily pull loose from the coil.
Once the boot is removed the spring and resistor will need to be removed from the coil. It to pulls loose but sometimes takes a little more effort. It will also pop the end of your fingers a little. Do not feel great but doesn’t really hurt. At lest hardened old hands. the new spring assembly needs to be fully pushed on the terminal inside the end of the coil. I normally line it up and the using a straight line force, compress the spring and seat it into the coil.
I also use a damp shop rag and wipe the dirt from the coil while inspecting for arc marks and cracks. If I find any that are suspicious, I prefer to change them but If needed I will just locate it to a cylinder position that is easy to remove.
Some of the coils require using a swivel or universal socket to remove and install the screws. When installing the screws, try to only use your fingers to start them and make sure they start easily. They screw into brass inserts that are very easy to cross thread.
Now that the coils are removed, I blow more dirt from the spark plug tubes. You would think as much as I had already blown the dirt off of the engine that it would be fairly clean. If you look closely you can see the sand being blown about.
Various extension lengths and a good universal socket will be needed to get all of the spark plugs out and back in.
The original is on the right and the new plug is on the left. It is easy to see if a spark plug is the original on a Ford product because they put paint on the tip at the factory. No paint and the spark plug has already been changed.
I try to always use a torque wrench when installing spark plugs. Sometimes there just isn’t enough room but this car has plenty. By the way the torque specification is 11 ft lbs.
I finished putting this one back together and took it for a test drive. All is well and no codes.