Codes P0172 and P0175, engine running rich?

I bet the cause for the engine's running rich is a partially clogged catalytic converter. This will cause the PCM to think the engine is under load (low vacuum) and dump more fuel even though there is no load. This guide can help you confirm this is the issue:

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

Please run down this guide and report back.

Thanks for getting back to me, I ran down the list right now. results are below.

Temperature readings

1st reading
1st cat 2nd cat
Inward 350 F 451 F
downward 451 F 421 F

2nd reading
1st cat 2nd cat
Inward 338 F 412 F
Downward 320 F 308 F

Ran motor without upstream 02 sensors
It sounded like a Harley, It didn't sputter or anything at idle . As far as power it seemed the same when I drove it around the block

Vacuum pressure gauge
It was at 21" , with the quick rev at the throttle the dial dropped to zero for a split second and went back to 21"

kept it at an rpm for about 15 seconds and the vacuum rose to 23 " then dropped to 21"

According to the temp test maybe my second cat is partially clogged? the other tests seem as though it passed.

Yep, the second cat seems partially plugged which will cause the issue. The power will be about the same with the sensor out because the hole is too small to let the exhaust out enough to see a difference. Also, the MAP/MAF sensor is still reading low vacuum. It could be caused by a stuck injector on the #2 side of the cat, I would remove the spark plugs on that side to see if one looks different than the rest.

The vacuum seemed as though it was where it was supposed to be according to the test 21 " at idle, held at 23" with an RPM of 2.500 or so. It only dropped to zero when I did a quick rev. is it still considered low? or should i re-do the test to confirm?

Also, wouldn't the computer throw a code if a fuel injector was faulty?

I'll take a look at the spark plugs as soon as I get a chance.

Thank you for the help thus far. Any more info is much appreciated.

The computer can only see the electrical portion of the injector not the mechanical valve part. Let me know what the spark plugs look like. The vacuum reading looks okay at idle, you can redo the test when the engine is under load it might tell us more.

I checked the plugs on bank 2. They were replaced a year ago. They look okay, a little white at the ends meaning maybe overheating a little. I tried attaching an image not sure if its showing.

Also, I tried the old screwdriver to fuel injector trick, they all seem to be working.

Okay, they look the same, can I ask if there is an exhaust leak on bank 2?

There's no exhaust leak that I could see.

I also wanted to point out that when the first check engine light came on it was the codes P0171 and PO174 (lean). I found the throttle body hose out to the purge solenoid was withered (Purge solenoid replaced later) I went ahead and replaced it, but the engine light remained on. When I checked the codes and tried to fix (sometime later) the codes changed to p0172 and p0175 (running rich).

Is it worth replacing the two catalytic converters? It's about $500.00 for all of it but the exhaust has to be welded.

Before we do that lets run the vacuum leak test again with the engine cool. here is a guide to show you how, check the PCV line these vans had a problem with them:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Please go over this guide and report back.

I haven't done the vacuum leak test again yet, but I did notice this. The pic is attached. This looks like the EGR valve. It is connected to the intake manifold. The bottom connection from the EGR valve is to the valve cover. The rubber connection to the valve cover is broken ...exposing the top of the valve cover (oil leakage). I'm not even sure what the part is or how to repair it. If you happen to know what is let me know. This can't be good for vacuum?

Yep, this is not good, the grommet needs to be replaced which should pull out of there using a large flat blade screwdriver. Let me know what happens please.

Hi,

It ended being the PCV. I replaced it and no change.
I sprayed brake cleaner around brake booster lines, intake vacuum lines, as well as the intake manifold. There seems to be no leaks. There wasn't a change in idle or anything.

In addition, I checked fuel pressure again. It was within spec.
Did a leak down test. After 5 min the pressure dropped to about 3 PSI. according to the manual that is also within spec.

re-did vacuum gauge to the intake manifold, it was around 20 in HG.


Further,

Here some additional info on the code:

I took a scan tool to the Ford to look at the freeze frame data of the DTC code.

FUEL SYSTEM CL
calc load 15.3
ECT 190
LTFT B1 -21.2
STFT B1 0
LTFT B2 -25.0
STFT B2 -.08
RPM 1996
VEH SPEED 65 MPH


I'm going to check my MAP sensor next, not really sure how to test it yet.

Any more ideas? more tests?

I was going to suggest the MAF sensor which the only way to test it is monitoring the value with a scanner against a new sensor. Here is the location of the sensor so you can swap it out.

REMOVAL AND INSTALLATION

CAUTION: Sensing elements located within mass air flow sensor should not be tampered with.

The Mass Air Flow (MAF) sensor is located between the engine air cleaner and the throttle body.

The MAF sensor electronics module and body are calibrated as a unit and must be serviced as a complete unit. Tighten sensor-to-bracket screws to 4.7-5.0 Nm (42-44 lb in).

Check out the images (below). Please let us know what happens.

Hello,

I did happen to replace the MAF a while ago.

With a SCAN TOOL MAF was reading just over 1lb of air per min at idle, and about 6-7 lbs around 2500 rpm (on the highway).

Those reading sound low, can you check to make sure the MAF is correctly mounted and there are no leaks in the air intake tube?

I ran a smoke test on the vacuum system. There is a decent leak around where the air filter housing is at. It seems the air filter gasket is too thick, and the top of the housing doesn't clamp down tight enough.

Also, I ended up doing a couple tests on my exhaust system. I found out there is a leak right after my rear 02 sensor (after the cat) and right before the muffler.

I'll try to fix it and report back.

Good catch, let me know if that helps.

I patched up the exhaust and did another smoke test. I didn't see any more leaks.
The air filter housing still leaks a bit despite clamping it down with some bungees. Van is still running rich. My long-term fuel is showing a maxed-out value of -25 on both banks at idle and around -20 when coasting on the highway.

Yep, it sounds like you have a fuel injector that is sticking. I would remove the spark plugs to see which one is black. This will be the cylinder the injector is bad on; you may have more than one injector causing the issue. Please let me know.

Checked the plugs they all look the same Ill post a pic a little bit later. I pulled the injectors anyways and cleaned them all. Runs the same.

Did you test the injectors?

Here is a guide to help:

https://www.2carpros.com/articles/how-to-test-a-fuel-injector

Please go over this guide and get back to us.

I went over the guide. Everything seemed okay.
I checked power from the PCM to the fuel injector connector both neg and pos.
Each fuel injector had an ohm reading of 15 ohms for all 8.

checked each injector with fuel pressure regulator results are below
each burst was 3 seconds of fuel.

cylinders 1 2 3 4 5 6 7 8
before psi 32 32 32 32 32 32 32 30
after psi 18 18 18 18 18 18 18 18

fuel pressure check
psi check
psi time
34 5:45
32 6:00
24 6:53

next morning @ 7:51 psi was at 0 then rose up to about 10?

Now the van is still running rich, and there is an idle issue it tends to stall when in drive or reverse lol. Battery voltage drops and you can hear the motor bog down. IAC and throttle body have been replaced and still same result.

Here are the fuel pressure specs, it sounds a little low and have you changed out the fuel filter? Check out the images (below). Please let us know what you find.

fuel filter was replaced already.

I am wondering if you have an EVAP purge solenoid stuck open, here is the location so you can check it out, you should not be able to blow through it off of the vehicle. Check out the images (below). Please let us know how it goes.

That has also been replaced. I've checked it while running and there is no leak from it. I replaced it a while back that's why I posted this thread, the shop I went to thought it was the solenoid as well.

The diagnostic trouble codes (DTCs) P0172 and P0175 indicate a rich air-fuel mixture condition in the engine cylinders of your 1996 Ford E-Series van. These codes are specific to fuel trim system bank 1 and bank 2, respectively.

Here's what these codes typically mean:

P0172 - System Too Rich (Bank 1): This code indicates that the fuel mixture in the engine cylinders of bank 1 is too rich. It means that there is more fuel in the mixture than the engine control module (ECM) expects, based on sensor readings. Possible causes could include a faulty oxygen sensor, a malfunctioning fuel injector, a dirty or clogged mass air flow (MAF) sensor, a restricted air filter, or a problem with the fuel pressure regulator.

P0175 - System Too Rich (Bank 2): This code indicates a rich fuel mixture in the cylinders of bank 2. The causes are similar to those mentioned for P0172, but they specifically affect bank 2 of the engine.

To diagnose and resolve these issues, you can take the following steps:

Check the oxygen sensors: Inspect the oxygen sensors for proper operation. They provide feedback to the ECM regarding the air-fuel ratio. If they are faulty or worn out, they may need to be replaced.

Inspect the MAF sensor: Ensure that the MAF sensor is clean and functioning correctly. Clean it if necessary or replace it if it's damaged.

Check the air filter: A dirty or clogged air filter can affect the air intake and lead to a rich fuel mixture. Replace the air filter if it is dirty.

Verify fuel pressure: Check the fuel pressure to ensure it is within the manufacturer's specifications. A malfunctioning fuel pressure regulator can cause rich fuel conditions.

Inspect the fuel injectors: Test the fuel injectors for proper operation. If they are faulty or clogged, they may need to be cleaned or replaced.