Cant figure out P0172 and P0175 codes

[goshdonutkaren]

Hello everyone, first post here, thanks for having me. I am having trouble trying to figure out what the cause of my check engine light is on my 1997 Ford Ranger with the 4.0 V6 4wd manual. The codes that pop up are P0172 and P0175, Bank 1 rich and Bank 2 rich. Here is a list of all the parts I have recently replaced:

-Fuel pump
-Fuel filter
-Fuel pressure regulator
-Upper plenum gasket
-Spark Plugs
-Idle Air Control Valve
-MAF
-Air filter
-PCV valve
-Vacuum hose from intake tube to oil filler neck
-PCV valve hose

I check fuel pressure and it holds right around 35psi, and I did a smoke test through various vacuum lines, the fuel tank, and exhaust. The only place I saw smoke come out of was at the front of the air box, and the exhaust flange right after the post cat O2 sensor. I also do not smell gas in the FPR vacuum line. When I check the freeze frame data on my scanner I get the following:

Short term fuel % trim Bank 1 = -3.125%
Long term fuel % trim Bank 1 = -25%
Short term fuel % trim Bank 2 = -3.906%
Long term fuel % trim Bank 2 = -25%

Lastly when I look at my MAF sensor readings while idling, I read around 4.6 g/s (I may have the units wrong, don't kill me). I honestly have no idea what else it could be at this point and would appreciate any other feedback or suggestions. If I missed something please ask and I will answer best to my ability. Thank you

 

[superj]

welcome!!

i am just here for moral support. the guys who can actually help will be on a in a bit

 

[Mechrick]

Always better to see rich codes than lean codes, the list of possible causes is much shorter.

FPR and MAF are the most common causes, you replaced them already.

Make sure the O2 sensor connectors haven't been accidently swapped left to right.

You could have dripping injectors. You can check by lifting the fuel rail/injectors out of the intake far enough to slide some newspaper under them. Pressurize the rail with a couple of key cycles without cranking the engine and see if fuel wets the paper.

While you are in there make sure the part numbers for the injectors are correct to the vehicle.

Is the air intake tract from the air filter to the engine factory parts?

 

[goshdonutkaren]

Always better to see rich codes than lean codes, the list of possible causes is much shorter.

FPR and MAF are the most common causes, you replaced them already.

Make sure the O2 sensor connectors haven't been accidently swapped left to right.

You could have dripping injectors. You can check by lifting the fuel rail/injectors out of the intake far enough to slide some newspaper under them. Pressurize the rail with a couple of key cycles without cranking the engine and see if fuel wets the paper.

While you are in there make sure the part numbers for the injectors are correct to the vehicle.

Is the air intake tract from the air filter to the engine factory parts?

O2 Sensors shouldn't be swapped, never touched them. Ill give the injectors a look and try that. Everything on the truck is bone stock. Before I replaced the IAC, i was getting the opposite codes. P0171 and P0174 system too lean. The second I replaced the IAC it swapped to what I have currently lol.

 

[goshdonutkaren]

Looking to hopefully revive this and get some more insight on this. I smoked tested the entire truck and didnt see any visible leaks anywhere. Replaced the spark plug wires and pulled the plugs to see if they were black. They looked great and nothing for concern. Did another fuel pressure test and was holding 30psi steady the entire time. Even after shutting engine off nothing dropped. Below is a picture of the freeze frame data for when the codes were recognized.

 

[rumblecloud]

I realize the O2 sensors have nothing to do with your issue, but since you've replaced everything else, why not go ahead and replace those too? Not sure what your mileage is but it's gotta be well past the recommended amount suggested for a change.


Welcome to TRS>

From your post it shows you know what you are doing - more than I can say for myself

 

[goshdonutkaren]

I realize the O2 sensors have nothing to do with your issue, but since you've replaced everything else, why not go ahead and replace those too? Not sure what your mileage is but it's gotta be well past the recommended amount suggested for a change.


Welcome to TRS>

From your post it shows you know what you are doing - more than I can say for myself

I went to replace them yesterday and ended up shattering the O2 sensor socket. Since I need to get the truck inspected, I plan to hold off on them just incase something goes wrong and creates a bigger issue. I am gonna try a new EGR valve today I think. If that doesnt work, then I will replace lower intake gasket as well as the fuel rail gasket and fuel injector o-rings.

 

[Mechrick]

Make sure the carbon canister isn't full of fuel and the canister purge valve isn't sticking open...

 

[goshdonutkaren]

Make sure the carbon canister isn't full of fuel and the canister purge valve isn't sticking open...

I will give them both a cleaning this afternoon, thanks.