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5.4 l 2v P071 & P0174 high lean long term fuel trims bank 1 & 2, Low power under load

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5.4 l 2v P071 & P0174 high lean long term fuel trims bank 1 & 2, Low power under load

 
  #31  
Old 07-18-2019, 10:29 AM
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Originally Posted by 150R View Post
Long Term ,will learn lean condition over time, A quick current draw and oscillation check with a scope pattern can tell you a lot with out getting the fuel all over the place.
LT ST is like the old GM block learn and integrator

you can do the current draw at the inertia switch,
voltage drop the ground toojust to be sure
I don't have a scope to perform the oscillation test. I have a digital volt meter and OBD Fusion on my iPhone.
 
  #32  
Old 07-18-2019, 10:49 PM
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MAF Volumetric Efficiency Test

I believe that I have a bad MAF according to all the tests and eliminations that I have done.

I ran the volumetric efficiency test with the OBD scanner connected to the iPhone. I did 4 separate tests at WOT for approximately 4 seconds. My starting speed was approximately 20 MPH for each test. I logged intake air temperature, RPM, and MAF flow rate using an online volumetric efficiency calculator. I performed the test on a flat road. It's not like this is real science.

I had a feeling that the MAF was bad because there were no vacuum leaks, the fuel delivered seemed normal, and both banks 1 & 2 had high long term fuel trims greater than 22%.

Rather than swap out parts, I did my best to eliminate what was not causing the problem. I have a new Ford MAF that I will install tomorrow. Even with high LTFT, the engine has not thrown a code in 200 miles driving. I am doing everything I can to make the engine throw a code. Not even a pending code was thrown.

Test 1 60.4%

Test 2 65%

Test 3 61%

Test 4 60%

Volumetric efficiency should be 75% or greater.






 
  #33  
Old Yesterday, 11:39 PM
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I installed the new MAF and immediately felt the difference driving. I connected OBD Fusion to my iPhone and noticed that the Long Term Fuels trims never go much higher than 12% even when driving WOT up a grade. I drove the van 13 miles and am pleased with the performance. Feels like a new van again!

It took me 1 month of testing and studying using fuel trims for diagnosing problems.

The calculate volumetric efficiency driving up the steep grade was over 80%.

After owning the 5.4 for nearly 3 months, I feel more confident diagnosing problems than I did on owning the 6.0 PSD for 4 years.

 

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