My 1999 ford taurus is fouling no. 6 plug with gas, what causes it to do that?

My 1999 ford taurus is fouling no. 6 plug with gas, what causes it to do that? - 1

Weak spark, no spark, or bad spark plug.

Do a full tuneup.

Leaking/bad injector or no spark. So bad wire or other condition causing that.

I had this problem once and solved it just by changing the spark plug. If this doesn't work. Get a professional tune up; if it would cost more than $500.00, Junk it. When an old Taurus starts giving trouble it can make you pauper. Trust me.