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Codes P0172 and P0175, fuel problem?

Tiny
KINGJD123
  • MEMBER
  • 2011 DODGE RAM
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 157,000 MILES
When I turn it on it struggles a little and then idles rough but will stay on but then if I press accelerator down let it go it wants to shut off. My fuel trim is showing -34 all my injector pulse are active and normal the
DTC code I got was p0172 and p0175 I was think vacuum so I changed all intake gaskets and check vacuum I have pics of what those show I reset codes and they haven't come back but it is still dying after I hit accelerator also I am not having any misfires.
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Friday, April 5th, 2024 AT 7:41 PM

7 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,264 POSTS
Hi,

Are the fuel trims still the same? As far as a neg 34 STFT, that indicates the PCM is trying to cut the amount of fuel to the cylinders. Often, that is a result of a faulty fuel pressure regulator. Have you checked if the pressure is within the manufacturer's specifications? If not, that is where I would start.

Here is a link that explains in general how to check it:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

I attached the manufacturer's fuel pressure specifications below.

Let me know what you find or if you have other questions.

Take care,

Joe

See pic below.
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Friday, April 5th, 2024 AT 8:46 PM
Tiny
KINGJD123
  • MEMBER
  • 99 POSTS
Just checked it and it is in spec. What is the next you would try and yes they are still negative?
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Friday, April 5th, 2024 AT 8:59 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,264 POSTS
Hi,

The next thing to check is how quickly the fuel pressure drops off when you turn the key off. There could be an injector issue (leaking). Also, make sure there are no air restrictions between the air filter and throttle body.

Let me know.

Joe
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Sunday, April 7th, 2024 AT 6:21 PM
Tiny
KINGJD123
  • MEMBER
  • 99 POSTS
Fuel is good and no leaking.
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Friday, April 19th, 2024 AT 7:36 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,264 POSTS
Hi,

I went back through the pics you attached above. I didn't notice any for the engine coolant temperature sensor. Before starting the vehicle, what signal is the ECT sending to the PCM?

Let me know.

Joe
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Friday, April 19th, 2024 AT 8:38 PM
Tiny
KINGJD123
  • MEMBER
  • 99 POSTS
ECT is reading valid outside temperature I thought it could be IAC Valve so change throttle body same problem could the intake runner make it run rich on both banks. When I was cleaning intake, I took the runner off.
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Friday, April 19th, 2024 AT 8:42 PM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,264 POSTS
Hi,

Anything is possible. A failed runner can cause air/fuel mixture issues. The runners are actuated under full throttle, so it could be related.

Have you had a chance to inspect them?

Let me know.

Joe
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Saturday, April 20th, 2024 AT 9:58 PM

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