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Codes P0172 and P0175, engine running rich?

Tiny
VANS89
  • MEMBER
  • 1996 FORD E-SERIES VAN
  • 5.8L
  • V8
  • 2WD
  • AUTOMATIC
  • 180,000 MILES
Hello,

The van listed above is an E250. The engine light is on and won't pass smog. Pulled the codes P0172 and P0175 (running rich?). I did take it to a mechanic for a diagnostic and they told me it was the purge solenoid. I paid for the part installed and still have the same problem.

symptoms: Starts up like a champ, when warm it seems sluggish hard to keep it at 65 MPH seems like its struggling. Runs okay at 55 and below. It has stalled before (even seems like its missing when at idle until I give it gas). I do see black smoke coming out of the exhaust when at idle. With the throttle wide open is runs okay. Still seems sluggish.

I've also replaced the following:

Fuel regulator
Fuel filter
MAF sensor
New air filter
New spark plugs
New air filter
Fuel pump read 30 PSI at idle
Purge solenoid

Anything else I should check?

Next, I plan on replacing the rubber hoses to the purge solenoid as they look corroded. Also, I noticed that the PCV grommet that fits on the right side of the valve cover is unsealed. I'm trying to figure out a way to replace this as its underneath the air intake. Do I have to take off the entire intake just to replace the pcv valve grommet? Anyone know a better way? Can this be the reason the motor is running rich?

Any help would be much appreciated.
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Wednesday, August 24th, 2022 AT 7:16 PM

27 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
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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.
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Thursday, August 25th, 2022 AT 12:48 PM
Tiny
VANS89
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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.
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Saturday, August 27th, 2022 AT 6:46 PM
Tiny
KEN L
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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.
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Monday, August 29th, 2022 AT 12:30 PM
Tiny
VANS89
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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.
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Monday, August 29th, 2022 AT 9:52 PM
Tiny
KEN L
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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.
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Tuesday, August 30th, 2022 AT 1:10 PM
Tiny
VANS89
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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.
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Sunday, September 11th, 2022 AT 9:44 PM
Tiny
KEN L
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Okay, they look the same, can I ask if there is an exhaust leak on bank 2?
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Monday, September 12th, 2022 AT 6:41 PM
Tiny
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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.
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Monday, September 12th, 2022 AT 9:52 PM
Tiny
KEN L
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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.
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Tuesday, September 13th, 2022 AT 9:23 AM
Tiny
VANS89
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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?
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Wednesday, November 9th, 2022 AT 9:00 PM
Tiny
KEN L
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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.
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Friday, November 11th, 2022 AT 1:55 PM
Tiny
VANS89
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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?
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Tuesday, February 7th, 2023 AT 9:09 PM
Tiny
KEN L
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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.
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Thursday, February 9th, 2023 AT 9:48 AM
Tiny
VANS89
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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).
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Wednesday, April 12th, 2023 AT 7:56 PM
Tiny
KEN L
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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?
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Thursday, April 13th, 2023 AT 11:57 AM
Tiny
VANS89
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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.
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Thursday, April 13th, 2023 AT 7:40 PM
Tiny
KEN L
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Good catch, let me know if that helps.
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Saturday, April 15th, 2023 AT 10:02 AM
Tiny
VANS89
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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.
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Monday, April 24th, 2023 AT 9:03 PM
Tiny
KEN L
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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.
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Tuesday, April 25th, 2023 AT 8:52 AM
Tiny
VANS89
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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.
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Monday, May 22nd, 2023 AT 3:46 PM

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