I have had an issue with my engine running rich with a cloud of gas behind me at every intersection. I just changed the plugs and noticed the plugs are black on the drivers side cylinder head. My first thought is that the O2 sensor is bad. The pssnger side has a new o2 sensor i saw. The drivers side o2 looks old and rusty. Check engine light comes on about every 5 minutes and shuts off. Any thoughts? Don't think its the coils.

-1991 lincoln TC limo. 4.6L.

 

I have a feeling it's the drivers side cat. It appears to have the symptoms of a bad cat. The cat on the psnger side has been replaced a few years ago and the car sat. Think I'm going to drill some holes in it so it doesn't cause any damage to my car, atleast till I get it replaced. First thing I'll do is scan the codes.