Have a 2008 F150 with the 4.6L engine and I'm having 2 problems. The car stalls frequently at idle. When I stop at a light or pull into a parking lot etc.. the engine will surge and then stalls. When I drive at highway speeds it doesn't stall or surge at all. Problem 2 is I'm burning through a lot of gas. Engine light is on and 2 code are present P0172 System Too Rich Bank 1 and P0175 System Too Rich Bank 2. 3 different mechanics have looked at the vehicle and can't find the cause for either. Any thoughts? Below is a list of parts that were replaced. I have a Ford OEM scanner but not really sure what to look for. I can see the RPMs surging from 300-1000 at idle but then it just dies.

Exhaust Manifolds
Spark Plugs
MAF Sensor
EGR Valve
PCV Valve
Both upstream O2 Sensors

 

Have you replaced the air filter? Check for excessive fuel pressure with your scanner, it's PID 168c. If it's high, could be the FPDM. You might have leaky injectors.

 

Yes, air filter was replaced as well as the FPDM with the updated standoffs. The fuel pressure reads nominal.