'90 PA error code 13, runs very rich!!

Hello everyone,

I'm the proud owner of a '90 Park Avenue with 70K miles. I'm experiencing a rich fuel mixter and can't figure out what would cause it.
The service engine soon light is on every so often, exhaust blows a lot of black smoke, pulled error code 13 (oxygen sensor), which makes sens to me since she's running rich.
Also when cruising at about 45 mph the engine is jerking. I've already changed the obvious O2 sensor, fuel pressure regulator, plug wires+plugs and the complete exhaust system including catalytic converter (old exhaust was rusted thru).
Any ideas or suggestions are highly apreciated.

Thanks

Welcome to AF. 13 is usually a bad sensor or connector to it.

I forgot to mention that I changed the O2 sensor as well.