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2004 F-150 running rich: P0172/P0175

  • Tacitus043
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20 Sep 2018 14:42 #23418 by Tacitus043
2004 F-150 running rich: P0172/P0175 was created by Tacitus043
Hi guys,

I have a customer with a 04 F-150 (5.4L 3v) that is running very rich and throwing P0172 and P0175. The engine runs slightly rough at idle but drives and cruises fine. I still need to figure out how to upload data graphs but here is some info I pulled from my scanner, as well as some tests I have performed.

-Fuel pressure PID is 40psi (confirmed with mechanical gauge). This particular system is returnless.
-LTFT's on both banks jump very quickly to -27 / -30 as soon as vehicle enters CL.
-Vacuum is 20in-hg at idle as well as 2500 RPM with no flutters or erratic needle movement
-MAF is ~6.5 g/s at idle
-BARO is 29 in-hg
-spark advance at idle is 15 degrees plus or minus 2
-back pressure measured at 02 sensor port less than 1psi at idle, as well as 2500 RPM
-compression is 200 psi across all cylinders

Before the customer brought the vehicle to me, the customer changed out all the oxygen sensors, plugs, and coils in an attempt to remedy the problem. This truck has me scratching my head so far, as I cannot put my finger on a particular part or system. I figured I would give a shout out to you guys and see if you had any advice on what diagnostic route I should take next. Thanks!

-Will

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20 Sep 2018 15:24 #23420 by BrianGee
Replied by BrianGee on topic 2004 F-150 running rich: P0172/P0175
If this has a vacuum controlled fuel damper I would pull the hose and check for fuel leakage getting sucked into the intake.

Do the LT fuel trims clear up at 2500 rpms?

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20 Sep 2018 15:26 #23421 by chief eaglebear
Replied by chief eaglebear on topic 2004 F-150 running rich: P0172/P0175
hi not a lot of experience here I would do an amperage on the fuel pump see what that should be also a volume test on fuel pump might have a better idea of whats going on and also stft is important in relation to ltft so it would be good to know that to geta better picture of what happening ltft tends to be an integrator so something is knocking trims off but we need more info I think ben and tyler and graywave are really good

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20 Sep 2018 16:13 #23422 by Tacitus043
Replied by Tacitus043 on topic 2004 F-150 running rich: P0172/P0175
LTFTs do zero out quickly as the engine is revved up. I did check the vacuum line going to the fuel pressure sensor and I did not notice any raw fuel being sucked through.

Also, I forgot to add, I did check to make sure the purge valve was not stuck open, it is operating correctly.

Thanks for the help guys!

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20 Sep 2018 18:14 #23423 by cheryl hartkorn
Replied by cheryl hartkorn on topic 2004 F-150 running rich: P0172/P0175
what is the coolant temp sensor reading? also can you get the o2s to respond by making a vacuum leak?

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20 Sep 2018 18:42 #23425 by Tacitus043
Replied by Tacitus043 on topic 2004 F-150 running rich: P0172/P0175
As far as I can tell, the ECU infers its data from a cylinder head temp sensor, rather than a conventional ECT. The cyl head temp sensor is reading ambient at startup, and moves smoothly to operating temp once the engine is running with no spikes or drop outs.

I'll create an artificial vacuum leak when I get in the shop tomorrow and let you know what the O2's do, thanks.

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20 Sep 2018 19:45 #23426 by Matts Auto
Replied by Matts Auto on topic 2004 F-150 running rich: P0172/P0175
Wouldn't hurt to check crankcase vacuum at pcv valve or valve cover breather. Possible internal vacuum leak

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20 Sep 2018 21:01 #23429 by Tacitus043
Replied by Tacitus043 on topic 2004 F-150 running rich: P0172/P0175
I did disconnect and cap the vacuum line for the PCV to make sure it wasn't huffing fumes from the crank case and did not notice any change in the fuel trims.

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21 Sep 2018 00:05 - 21 Sep 2018 10:39 #23431 by BrianGee
Replied by BrianGee on topic 2004 F-150 running rich: P0172/P0175
..
Last edit: 21 Sep 2018 10:39 by BrianGee.

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21 Sep 2018 00:09 - 21 Sep 2018 10:38 #23432 by BrianGee
Replied by BrianGee on topic 2004 F-150 running rich: P0172/P0175
Removed for Alzheimer moment
Last edit: 21 Sep 2018 10:38 by BrianGee.

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21 Sep 2018 07:13 #23435 by Bealio
Replied by Bealio on topic 2004 F-150 running rich: P0172/P0175
Aren't positive trim numbers associated with vacuum leaks. We're seeing negative numbers according to Tacitus043.

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21 Sep 2018 10:37 #23439 by BrianGee
Replied by BrianGee on topic 2004 F-150 running rich: P0172/P0175
Lol, yeah. Long day..

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21 Sep 2018 11:04 #23440 by Tacitus043
Replied by Tacitus043 on topic 2004 F-150 running rich: P0172/P0175

BrianGee wrote: Lol, yeah. Long day..


No worries, I'm right there with you. I did check the intake gaskets and all the vacuum connections to the manifold and everything seems to be sealed very well.

Just some of my gut thoughts: when its idling it feels like a motor with the EGR valve stuck open, or severely retarded ignition timing. This particular motor uses them cam phasers to regulate EGR, however both cams seemed to be indexed perfectly relative to the crank. Maybe one of you Ford guys could chime in on some of the variable timing related PIDS; however the desired cam positon vs the actual cam positon are in agreement.

Also, could it be possible to have weak spark at idle, but be fine at high speeds and higher loads? In my experience the latter problems tend to be exaggerated with high loads.

I'm having to use a lot of my will power right now to resist throwing parts at this thing.

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21 Sep 2018 14:25 #23443 by Bealio
Replied by Bealio on topic 2004 F-150 running rich: P0172/P0175


Are the spark plugs fouled? Fuel soaked? Try an injector balance test.
Attachments:

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21 Sep 2018 20:21 #23444 by Weycraze
Replied by Weycraze on topic 2004 F-150 running rich: P0172/P0175
Just some quick questions..

1. Does the Fuel Pressure drop on snap throttle?
2. Once in CL what are LTFT's @ idle, 1500, and 3500 rpm? Also, are both banks identical or different? ( Do the trims go positive as rpm is increased?)
3. On snap throttle does your Vac guage return to 20 in HG quickly or slowly?
4. On snap throttle, what is the highest g/s the MAF can achieve?
5. Do you smell raw, unburnt fuel at the tailpipe?
6. What are your MAP PID values at idle, 1500 and 3500 rpm?
7. What are your CALC Load values at idle, 1500 and 3500 rpm?

If you scan tool has Bi-directional control, command the EGR to open at idle, engine should stall.

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22 Sep 2018 12:37 #23449 by Dave101
Replied by Dave101 on topic 2004 F-150 running rich: P0172/P0175
I agree with Weycraze.
Just make sure there are no vacuum leaks on the engine. I've had the back of the intake leak cause me problems such as this before.

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25 Sep 2018 21:53 #23509 by Seeger3
Replied by Seeger3 on topic 2004 F-150 running rich: P0172/P0175
I would recommend a closer look at maf sensor - 6 grams at idle fully warmed up is a little high ... Not way out of spec but since nothing else is suspect I would start there. With negative fuel trims you are not looking for vacuum leak. O2 sensor when it sees a vacuum leak (extra oxygen in exhaust) it will add fuel to compensate so u will see high fuel trim not negative. May start with cleaning maf.

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