2000 Ford Explorer po171 po174

Darren Technician Wisconsin Posted   Latest   Edited  
Unsolved
Driveability
2000 Ford Explorer Eddie Bauer 4.0L (E) 4-spd (4R70W)
P0171 — System Too Lean Bank 1
P0174 — System Too Lean Bank 2
MIL On

I live at 930 ft above sea level, just moved here.

What frequency should my baro be on this vehicle.

My reading is 153 hz…..

Obviously I suspect a maf sensor out of calibration ,

Of course I will follow proper testing methods,

like Bernie says, follow the data.

My question was very specific about the baro pid

at that specific sea level.

It has new intake seals and fuel pump from

another shop.

maf sensor is 3 grams per second at 650 rpm

long term fuel trims are adding fuel at 25 percent at idle both banks, and drop close to 0 off idle immediately.

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Stephen Owner/Technician
California
Stephen
   

I'd smoke check it, you may have leaky upper intake o rings. A cleaning of the màf would be helpful as well, Check fuel trims as you fog areàs with brake clean if smoke machine isn't avail. 155hz at 1000ft is the average

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Glenn Owner/Technician
Texas
Glenn
 

Hi Darren, It is too easy to suspect a MAF problem, but there is some testing needed to prove it's having a problem. The first thing I would suggest is to remove the MAF and clean the hot wires with some MAF cleaner or brake cleaner. Do not use regular carb spray because it will damage the epoxy doping on the hotwires. If it has a K&N filter, make sure it has not had too much filter oil…

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Helpful
Mark Engineer
Colorado
Mark
 

Darren Give us a little more info. Go into mode 06 data and I think it’s the second choice for freeze frame data for one of the two codes. Give us a few of the parameters

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Jay Technician
Nevada
Jay
 

I have to agree. I would be looking for intake leak first. Baro readings can be Inferred and May not update until next WOT. If you don’t have a smoke machine readily available you can use scan data. First look at LTFT and STFT at Idle and … rpm. If the LTFT corrects itself off idle you are probably looking at a vacuum leak. Use brake clean and watch fuel trims.

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Sean Owner
Arizona
Sean
 

I don't go by hz. I go by grams/sec. But first, you need to looks at fuel trims at idle, cruise, and acceleration to find out where your lean condition is. If it's only at idle, look for vacuum leaks. If it's only under acceleration, check fuel pressure next

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George Technician
Alabama
George
   

Check fuel pressure also! May need pump if it’s 22 years and hadn’t been changed.

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Glenn Owner/Technician
Texas
Glenn
 

Hi George and Darren, George, I tend to agree with you if the pump can be verified to have a fuel volume problem. Also, I would ask the obvious question: Has the fuel filter been replaced? These have one mounted to the inside of the frame under the driver side floorboard. Many people forget they still had inline filters back in those years. Currently I own 4 FMC vehicles of this vintage and…

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Paul Mechanic
Illinois
Paul
   

He stated it has new fuel pump and fuel trims correct off of idle, so I doubt it's fuel delivery.

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Alejandro Technician
California
Alejandro
 

Take a very good look at your PCV system hose. The rubber tend to deteriorate and cause a lean code.

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Jay Technician
Nevada
Jay
 

Sounds like a vacuum leak

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Sean Owner
Arizona
Sean
 

Vacuum leak.

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Ted Owner
Texas
Ted
 

Once you fix your vacuum leak, reset KAM to allow fuel trims to recalibrate (i.e. not be skewed by previous conditions and saved data).

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Glenn Owner/Technician
Texas
Glenn
 

Hi Darren, Here is a Baro chart at the end of this TSB I found. Baro charts are not vehicle specific. Looks like you are close the correct reading. At 1000 feet it shows 156 Hz. on the chart. I suggest once again to clean the MAF hotwires. After that reset the KAM and go from there.

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Rusty Owner/Technician
Massachusetts
Rusty
 

A dirty MAF would show rich at idle and lean at higher RPMs. Your symptom strongly suggests a vacuum leak however I recall a trimming issue on those trucks when the air cleaner cover would get distorted and fail to properly seal. It’d upset the laminar airflow across the MAF. I can’t recall if it affected the measurement at idle or with speed but it’s worth a look.

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Timothy Owner/Technician
Wisconsin
Timothy
 

At 930 ft. you're MAF/BARO number looks very close to spec. In my area (about 630 ft.) I routinely see about 156 or so, on a tight engine. This has got vacuum leaks, judging by your low MAF g/sec, despite the intake seals being replaced. If they just did the upper plenum and not the whole lower intake seals, that could cause it. These update BARO on acceleration and at WOT and start-up, but…

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Eric Manager
Arizona
Eric
 

Check anything that can effect MAF reading. General rule is at 600 rpm, neutral and no A/C, MAF grams per sec should match engine size. You are at 650 and 1 gram low.

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