Good afternoon...

• I am having these codes show up on 2008 Saturn Aura 3.5:
• P0301 Cylinder 2 Misfire Detected
• P0172 System Too Rich Bank1 Status: CURRENT System Too Rich Bank1

Here is what I did:

• Changed all fuel injectors
• Changed Plugs
• Changed Plug wires
• Checked wiring harness
• Cleaned MAF Sensor
• Swapped plugs from 2 to 4
• Swapped plug cables from 2.to 4
• Tried a different Ignition coil from another vehicle
• Checked compression
• Cleaned harness connections

What came first the chicken or the egg...
In my mind if I have a cylinder misfire, it might dump raw fuel into the cylinder to carry downstream where the O2 sensor detects too rich... again, only my thinking on this...
Or could a bad O2 sensor cause a problem where it tries to make a correction and causes Cylinder 2 to misfire. The misfire is legitimate, I can feel it... The vehicle starts, runs perfect, but gets to a point within only a few minutes where the scanner starts accumulating misfire counts.

Any ideas???
Thanks,
Steve

I'm sorry to tell you this after so much troubleshooting, but P0301 is misfire on cylinder 1.

I'd start by checking fuel pressure with a real gauge on the fuel rail.

Your approach to fixing this is such that I can only suggest you take it to a shop.