Lincoln/Mercury Repair: 99 Mercury Cougar Starter Grind, mercury cougar, gas milage

Question
I own a 99 Mercury Cougar that likes to have an inconsistent starter grind.  Like the starter is grinding against the flywheel.  It would only do it 1 in 15 starts.  It seemed to help to wait and listen for the fuel pump to engage then it would start.  I figured it was the starter going out.  I replaced it with a new one and the situation improved. Now the new starter is doing the same thing more like 1 in 50 starts but still doing that grind.  I don't know if it has anything to do with it but the Check Engine Light comes on and the code they pull says the car is running lean like I need to replace the O2 Sensor.  I just really want the car to stop grinding at suprising times and embarassing the hell out of me.  If there is some electrical circuit or sensor gone bad or something I don't know that would cause this please let me know.  I need help and I would thoroughly love a suggestion.  Thanks in advance.

Answer
HI Caleb,

The grind is missing or damaged teeth on the flywheel. This can be an expensive repair due to the transmission must be removed to replace it. Of course, this is damaging the starter teeth also.

The O2 sensor has nothing to do with this, but your car will get better gas milage and run better the sooner you have that O2 sensor replaced.