+1 on the compression test. It's free since you'll get your money back once you return the equipment.
How long have you had the Mark? I don't suggest throwing money at vehicles but I always do a complete tune-up when I purchase my Marks and might be required if you haven't done so already since acquiring your Mark VIII.
In case you don't know, here's what you'll need with ballpark prices(Rockauto/Summit Racing & local vendors).
- 8 spark plugs - $20-24 (Autolite 104s/764s*, Champion, MOTORCRAFT SP433s)
- 8 Coil on Plugs- $200-400 (DENSO or MOTORCRAFT*) or just the boots $10-15
- 1 PCV Valve - $2-5 (BWD or MOTORCRAFT*)
- 1 Fuel Filter - $8-15 (Wix or MOTORCRAFT*)
- 1 Air Filter - $10-16 (FRAM or MOTORCRAFT*)
- 1 Oil Filter - $3-10 (MOTORCRAFT FL-820S*)
- Oil Change $25-60 **(insist that they use your MC oil filter) or change your own
- 5 Quarts Synthetic Blend 5W-30 - $20-45 (Castrol GTX / Mobil 1 / MOTORCRAFT)
- *It may be cheaper to get a 5qt gallon rather than individual quarts
But first, before buying parts, check if infact it is the ignition coils by unplugging COPs 3 & 6 to notice any changes(or lack thereof) in the engine, or swap 3 & 6 with other cylinders to see if the code scanner follows the change. As noted, a set of 8 COPs can be quite costly($200-400), so maybe you can get away with just changing the
boots & coils($10-15) on all 8 Plugs to get rid of the "butter"(some call it ear-wax) that builds up on the coils inside the boots from oil saturation.
Check out this cat. His Continental sports a FWD version of the DOHC Intech and so his theory can be applied to the Mark VIII.
In my experience, Oil in the spark plug-wells is usually an indication that the tube-seals have expanded or contracted beyond their OE specification which will then allow oil to seep in. When you change the plugs, or have time & feel inclined, take a look at the top of the plug-wells to see if you notice any grey or black seals being offset(slightly exposed into the tube or pushed in) where the valve covers meet the wells.
Random pic with bad tube seal, notice the black grommet is not symetrical.
This is usually remedied by purchasing a new set of valve cover gaskets(
$30-50 Rockauto FEL-PRO*, a
bit more at local vendor) which they often come with 8 new tube-seals.
As for difficulty on the valve cover gaskets; You'll go into the job looking like youthful Private Ryan but will end up like old Ryan by the time you're finished with the driver's side valve cover.
So if you decide to tackle it, Google "
lincoln mark viii valve cover removal". The first few results should be from LVC and other similar sites where people have expressed their disapproval of FORD's engineering with this valve cover and added their own write-ups. Maybe you can do the passenger side and have the shop do the driver side...
Though the shop may insist that, "In order to ensure a job well done(of ripping you off), it's best that we do both sides(and charge you more than than you wish to spend). Otherwise, we can't do it." Let's not forget that they'll use the same gasket set you can get for 30-60 and want to charge you 75-100, not for the set but per gasket at that.