How to install spark plugs in a 94 3.8 V6 lincoln continential

check coolant level -oil level and condition if milky --but water in spark plug holes is an indication of blown head gasket --cracked head--block or intake

Do a compression test. Maybe that motor needs major repair.

Did you air them lately with a Air hose like your Tire ?

The spark plugs in the v6 can become an involved job as the upper intake manifold. The LS uses a Coil on Plug (COP) ignition system, meaning that the spark plugs are located under the ignition coil

If you raise the car up off the ground,and safely support it ,you can crawl under and find the leak. Or put it on a lift at ,a close by repair shop.

3.8 L engine
Use new cylinder bolt's
Apply sealant to shortest bolts.

Step #1 15ft.lbs
Step #2 30ft.lbs
Step #3 37ft.lbs
Step #4 back off all bolt's 2-3 turns
DO NOT loosen all bolt's at one time, work on one bolt at a time.
Step #5
Long bolt's
1st step 30-37ft.lbs
2nd step additional 175-185deg. turn
Short bolt's
1st step 15-22ft.lbs
2nd step additional 175-185deg. turn

It is located down by crankshaft. If you follow the spark plug wires down to the coilpack & module. Then from module straight to crank sensor

If the car is missfireing, don't try to patch it one plug at a time. go ahead and replace them all at once. It will save you 5 more cylenders to hunt later.

Most reputable chain shops will test your alternator FREE, call around to Pep Boys, Autozone, etc and ask if they will. 
Most of these problems are just poor maintenance, corroded battery terminals, aged battery.  Get someone to clean and tighten your battery connections and have that alternator tested if the problems persist.