I have a "slow o2 sensor", according to o'reilly's, i can't remember if it was upstream or downstream though. Also about every 6 months or so I have to replace the spark plug for cylinder one due to a misfire. The arc thing or w/e in the plug is just completely gone and the spark plug smells of fuel and/or oil. The o2 sensor problem comes and goes, I usually leave it and the check engine light will go away after a while. Is their any correlation between the two? Is their anything else this might be? I need some help.

 

I had the same problem about 10 miles after I switched to E3's on my 2.3. The length of the plug is the same but the seat where the plug sits on the block is just a bit lower. The plug boot on mine wasn't snapping on to the top of the spark plug like it did with the MotorCraft plugs. So when it heated up it popped off. That was the only cylinder it happened on so I trimmed the of the boot a bit. That made it narrower to fit down the spark plug valley further. I had problem with a K&N oiled air filter on my Mustang, I read it on two different web site that some oil can land on the sensor and get baked on it and cause slow reacting O2's. I went back to a paper filter on both of them.