I have a 1999 E-150 with a 4.6L with 30,000 miles on it. The codes P0172 and P0175 keep showing on my scan tool. Changed O2 sensors, costly mistake. Also blew out the return fuel line. Some good advice from you guys out there would be nice. Thanks

 

darkris,

1) Check/change your air filter. A dirty air filter or clogged intake system can cause a "rich" condition.
While your there clean your MAF.

2) Run some fuel injecter cleaner through. Reset your PCM.

If you get the codes again, have your fuel pressure tested. A bad fuel pressure regulator or check valve could be causing your rich condition.

Good Luck,

Bill