Is there a way to eliminate the problem? I have a PO172 Error

Question

Hello, I have been trying get the check engine light out.  My smog is overdue and I can't get the darn thing to go out.  I have done a full tune up, the O2 sensor.  Retested it with a code reader.  The light goes out then comes back on.  So now the code is PO172.  I am a trying to use the process of elimination for I am not that knowledgeable.  Is there any suggestions of how to eliminate the possibilities to pin point my problem.  I am not very mechanically savvy.  Thank you so much.
P.S. since I had the current work done my idle is above 1000rpms

Answer 1

Running rich condition is more a mechanical condition of the engine such as low compression on one or more cylinders. Check the fuel pressure regulator and see if fuel is seeping out of its vacuum port connection if there is fuel seeping out replace the fuel pressure regulator. Fuel pressure should also be checked, if the fuel pressure is low the fuel injector will not atomize the fuel , First is to rule out any mechanical condition such as the compression of the engine