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Sometimes it runs fine and then it will hardly idle and stalls?

Tiny
KDCHRIST
  • MEMBER
  • 2004 FORD F-150
  • 5.4L
  • V8
  • 2WD
  • MANUAL
  • 251,000 MILES
Upstream 02 sensors are stuck lean. I replaced the vapor canister purge solenoid and upper hose it was damaged. Did smoke test did not see other vacuum leaks.
Thursday, January 25th, 2024 AT 7:10 AM

34 Replies

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 108,277 POSTS
Hi,

Are any codes present? Also, does this only happen when the engine is warm, or could it do it when the engine isn't warmed up?

Let me know if you have a live data scanner. If you do, check the short-term fuel trims when this is happening. Also, check the coolant temperature sensor's signal to the PCM.

Try this and let me know what you find.

Joe
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Thursday, January 25th, 2024 AT 7:25 PM
Tiny
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Shrt ft minus 15 to minus 18 coolant temp sensor 188 degree.
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Friday, January 26th, 2024 AT 9:56 AM
Tiny
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02 sensors now reading stuck on rich.
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Friday, January 26th, 2024 AT 10:03 AM
Tiny
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FTP is 33-34 pst
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Friday, January 26th, 2024 AT 10:09 AM
Tiny
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  • MECHANIC
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Hi,

The trims indicate the PCM is trying to lessen the amount of fuel entering the vehicle. As far as the fuel pressure is concerned, it's at the threshold of being low (KOEO), which is confusing. I would have suspected the opposite. (See pic below)

Is it possible to get the codes you found?

Joe

See pic below.
Image (Click to make bigger)
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Friday, January 26th, 2024 AT 7:06 PM
Tiny
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Key in on position 40 PSI when running 32-34 PSI.
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Saturday, January 27th, 2024 AT 6:04 AM
Tiny
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IAT is 84 when warmed up.
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Saturday, January 27th, 2024 AT 6:07 AM
Tiny
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P0451, p0172 0175, and p02196 2198.
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Saturday, January 27th, 2024 AT 7:47 AM
Tiny
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See freeze frame.
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Saturday, January 27th, 2024 AT 10:46 AM
Tiny
JACOBANDNICKOLAS
  • MECHANIC
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Hi,

Where should we start? First, the fuel pressure appears to be good. There could be an injector issue. When you checked the pressure, did you take notice of how quickly it dropped when the key was turned off?

Next, have you checked for any restrictions on the air inlet system (air filter, inlet tube)? Have you replaced the oxygen sensors already? When was the last time spark plugs were replaced?

Don't laugh, but when this happens, does the transmission react differently?

Let me know. Sorry for so many questions. However, based on the codes, it could be something as simple as a plugged air filter and as extreme as the powertrain control module (PCM).

Let me know.

Joe
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Saturday, January 27th, 2024 AT 7:36 PM
Tiny
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They are 2 months old. I put in new upstream 02 sensors and put in a new air filter. The fuel pressure when up a little when the key was turned off. I started it last night and it was ruff at first then it ran smoothly, but the ideal was a little low. Code 0451 appeared pending This morning I started it. Nothing but rough running and stalling no codes appeared.
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Tuesday, January 30th, 2024 AT 7:33 AM
Tiny
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I started it this evening and rev it up right away and got it to run smooth with now collection of codes.
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Tuesday, January 30th, 2024 AT 4:44 PM
Tiny
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Hi,

Do you mean there is a new collection of codes? If so, are they different? Let me know. Also, let me know what they are.

Take care,

Joe
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Tuesday, January 30th, 2024 AT 8:04 PM
Tiny
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I meant no collection of codes. I will keep an eye on things.
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Wednesday, January 31st, 2024 AT 5:39 AM
Tiny
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I changed the upstream 02 sensors and the fuel filter. I removed the fuel rail and injectors. I reached down behind the engine and removed and cleaned and reattached the vacuum lines. I cleaned and replaced 1 injector and reinstalled them and the fuel rail. Started it and it ran fine. Test drove around the block fine. When a little farther and it bogged down and stalled. Managed to get back to the house. It seemed to ideal fine but revved up a little from time to time. Pulling P0171 I tried to add an image of freeze frame data, but it will not except a Microsoft edge file.
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Wednesday, February 7th, 2024 AT 12:30 PM
Tiny
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Hi,

I went through the diagnostics again. Everything they indicate is related to either a coolant temperature sensor or an engine vacuum leak for this code.

I attached the diagnostics below specific to the code. It starts at step H17. Take a look through them and let me know if you are comfortable performing them or if you have already done what is suggested.

Take care,

Joe

See pics below.
Images (Click to make bigger)
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Wednesday, February 7th, 2024 AT 4:19 PM
Tiny
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Freeze frame data p0172 present SHRT FT1- 4.7 HHRT FT2- Minus25.3 LONG FT1 minus2.3 LONG FT2- minus 20.3 at 3600 rpm Live data at ideal SHRT FT1- between 0 and minus 7.0 SHRT FT2- between 0 and minus 4.7 LNG FT1- minus22.7 LNG FT2- minus 21.1 both set of data @ ECT-188F IAT- 71F Does this tell us anything? I do have a full freeze frame data set.
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Saturday, February 10th, 2024 AT 10:55 AM
Tiny
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Hi,

the STFT bank 2 and crazy high. If that is a negative 25.3%, either we have a fuel injector leaking or a pressure issue. Am I reading that correctly?

Joe
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Saturday, February 10th, 2024 AT 4:54 PM
Tiny
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Yes, that is correct. The fuel pressure at the rail is pretty steady around 33 PSI. Could a bad fuel driver module? Before I changed the upstream 02 sensor everything was stuck lean now it is stuck rich. The symptoms remain the same. Running smooth and then it bogs down and won't idle.
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Sunday, February 11th, 2024 AT 4:49 AM
Tiny
JACOBANDNICKOLAS
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Hi,

The fuel pressure sounds good. So, when you checked pressure, did you pay attention to pressure drop-off? In other words, did they stay steady for a while when the pump was off, or did it drop rather quickly? I ask because we may have a leaking injector. Also, and I think I asked this before, but do you have any exhaust leaks upstream from the oxygen sensors? Fords are notorious for manifold leaks.

Let me know.

Joe
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Sunday, February 11th, 2024 AT 2:53 PM

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