Fuel system lean on 1 bank only

Charlie Owner/Technician Freetown, Massachusetts Posted   Latest   Edited  
Question
Driveability
2005 Ford F-250 Super Duty King Ranch 5.4L (5) 5-spd (TorqShift)—1FTSX21575EB68898
P0174 - System Too Lean Bank 2
B1 Ltft 2%
B2 Ltft 32%

Good afternoon,

Having an issue with this f250 truck that came from another shop for this code. Initial scan freeze frame data showed code set at idle. Monitored fuel data focusing on long and short term fuel trims and bank 1 and 2 upstream and downstream values. Bank 1 is perfect at 0 and bank 2 at +32.

I reset KAM and started vehicle from cold start found fuel trims on bank 2 climb right up once it goes into closed loop. Checked for vacuum leaks using smoke through intake. Found no leak at all​. ​Performed cylinder balance test but no issues found there. Performed injector flow test using scan tool and found both banks to have almost identical readings. Smoke tested through exhaust and found smoke coming out steadily through a crack in the drivers exhaust manifold. Thought sure this was the issue. Replaced exhaust manifold and reset KAM again started vehicle and monitored fuel trims again found the same issue. Within 5 minutes of idle the short term was +30 on bank 2 road tested and found that even during cruising and accelerating bank 2 stays positive while bank 1 stays relatively low never going above +8.

Thinking about doing a mechanical fuel injector flow test using a mechanical pressure gauge and an injector tester. Any other tests that i may be overlooking. Anybody had this issue with a ford before.

Thanks in advance for any input or assistance with this truck.

Charlie

+3
Interesting
Zachary Mobile Technician
Austin, Texas
Zachary Default
   

Hey Charlie, Sounds like you've done a fair amount of testing but I have some questions/suggestions. First, what's the year and engine size in this truck? Have you checked for any TSBs that may be related? Second, when you say the bank 2 trims stay positive on the test drive are they as bad as idle? Is it under all conditions or only once the truck settles into a cruise situation? Third, does…

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

The truck is a 2005 5.4l but it has a used engine that I have no history on but the writing from the junkyard appears to be a 2007 engine. The fuel trims on bank 2 do stay high even under a load they're not as high but still at least double bank 1 i don't believe the wires are crossed for the 0/2 because they don't look like they would reach. When I came back from road test it was way to hot to…

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Tyler Technician
Olathe, Kansas
Tyler Default
 

Hey Charlie! Does the bank two upstream O2 ever read rich? During WOT or while feeding it alternate fuel? Does the downstream O2 agree with the upstream O2 on bank two?

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

Upstream and downstream do agree with each other and under a load the fuel trim does get a bit better it does shift towards positive but still much less than bank 1. Also I hit the cats with a temp gun both cats are same temp and there's roughly 75 - 100 degree difference between inlet and outlet of both cats

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Eric Owner/Technician
Edgerton, Wisconsin
Eric Default
 

Can we at least get the year, maybe the engine size and type? A VIN would be nice if it's not too much to ask for.

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

First time asking a question on this site and started on my phone but things got deleted so moved to laptop didn't realize that it didn't post the vehicle info sorry I edited it but in case that didn't work here's the info 2005 f250 5.4l 3v. Vin # 1FTSX21575EB68898

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Justin Technician
Concord, California
Justin Default
 

I would look at the catalyst for a restriction sounds like it’s not flowing through properly good luck please let us know the outcome many requesters don’t give us updates

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

I will definitely post the final outcome I'm hoping to have it figured out tomorrow

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Robert Diagnostician
Fair Oaks, California
Robert Default
 

Have you done a power balance to see if all the cylinders are contributing the same? misfire can dump O2 in the exhaust causing positive fuel trims. If it is one bank, then is valve timing correct on that bank? Does the O2 sensor switch at +32 fuel trim? If that is all good, then I would be looking at injector restriction on that bank. Might try on car injection cleaner and see if trims improve.

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

Power balance was perfect. Once long term hits around 30 - 32 short term seems to stabilize if I put the 02 sensors on graph both upstream look almost identical as far as rate of switch but the right bank is just way more positive. Everything in my gut tells me the injectors on this bank are not flowing properly but the injector flow test through scan tool says they're the same as bank 1…

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Robert Diagnostician
Fair Oaks, California
Robert Default
 

I have seen injectors that flow bad at idle flow rate and flow better at part throttle rate. When we send our injectors out to DR. Injector they flow test them before and after cleaning at two different flow rates. Sometimes the injectors will flow ok at higher levels and be way off at idle level. If you want to test the injectors without cleaning or putting new ones in you could swap injectors…

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

I suspect that cracked exhaust manifold biased the O2 on that side. Graph both front O2 sensors and feed the engine little bursts of propane, through a central vacuum port. Both O2 should hit 900 mV instantly.

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

I will definitely give this a shot in the morning

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

any time I see trims out like yours, my first test is a FRTD, while graphing; fuel trims, oxygen sensor voltages, engine load, RPM & throttle position. After analyzing that data, kill the fuel pump and do a relative compression test, with a trigger on #1 ignition. Post the information up here, and the answer to your question will be easy to come up with.

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Todd Mobile Technician
Morinville, Alberta
Todd Default
 

Albin, you should tell Charlie what a Flat Rate Test Drive is.

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

OK, since you asked :). FRDT (flat rate test drive). Is where you can capture the much needed information all in one short test drive to tell whether the problem is caused by; valve timing issues, oxygen sensor issues, MAF sensor misreporting, Fuel quality issues, restricted air flow, whether it be in the exhaust or intake, and there are a few other things that haven't crossed my mind yet. Set…

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Helpful
Joel Diagnostician
Freetown, Massachusetts
Joel Default
 

I agree with Albin. You may have been able to eliminate or customize some pinpoint test for the conditions/fuel trim trends you are dealing with. Fuel trims high at idle and drop during load. Power brake the vehicle and eliminate engine vacuum while monitoring fuel trims will eliminate a vacuum leak issues. If Bank drops slightly but still stays high under loads you are most likely not dealing…

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Anthony Technical Support Specialist
Kirkwood, Pennsylvania
Anthony Default
 

Hi Charlie: It could be that Bank 1 had a restricted exhaust. It could be the O2 sensor connectors are swapped. (I was embarrassed when I did it.) I'd check the latter first. HTH, Guido

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Danny Technician
Frederick, Maryland
Danny Default
 

I believe there is a flex fuel option for that engine. I think the injectors are different colors for flex vs not and if a used engine is installed with the wrong injectors it has lean issues. Not sure why it would affect only one side unless only half of the injectors were swapped.

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Kirk Technician
Glenwood, Iowa
Kirk Default
 

Since this is a 3 valve 5.4 have you looked into timing issues? A quick way to roughly check timing is to get engine at TDC remove both cam sensors. Note the position of the trigger wheel in the cam sensor hole on the left bank. Blade should be approximately halfway point. Turn the engine over 360 degrees the trigger wheel on the right bank should be roughly in the same position in the hole. I…

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Albert Owner/Technician
Towanda, Pennsylvania
Albert Default
 

I'm interested in see the out come. I'm sorry I can't of any help You done all the test i would have I'm wondering is it's not a bad CO2, wiring or connection.

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Matthew Mobile Technician
Bartlett, Illinois
Matthew Default
 

I would put some propane in the intake running to make sure both bank 2 oxygen sensors go rich, remove propane and make sure they go lean. If the sensors are okay and you are lean at all engine loads I would suspect fuel delivery. Most of the time when your trims are consistently lean at all engine RPMs and loads it is fuel injector related. You can test primary ignition on those with a scope…

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Joel Diagnostician
Freetown, Massachusetts
Joel Default
 

If you did a WOT road test both bank should go rich (above 800mv) and all Oxygen sensors should react the same. During a closed throttle decel, fuel cut off all sensor should drop lean (below 150mv) and also react the same. Save and record this data so you can analyze it and graph fuel trim trends and max load. You can see bank to bank balance and reactions and also calculate VE with information.

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Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Chat is a great way to dynamically test the whole system. That's all part of a FRTD.

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Joel Diagnostician
Freetown, Massachusetts
Joel Default
 

Looking at the data you updated. It looks like you have a restriction on Bank1. The Bank 2 O2 sensors go lean under loads while Bank 1 hard a hard time staying above 800mv. The STFT shows the breathing issue. The VE is also slightly low.

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Robert Diagnostician
Fair Oaks, California
Robert Default
 

looking at your data file, bank 2 is going lean under load as you accelerate. That is not going to be a vacuum leak. A MAF sensor would effect both banks. Usually a valve timing issue on 1 bank will cause negative fuel trims as it does not breath as good. If it was a restricted exhaust with a mass air flow sensor, the bank with the restriction would have negative fuel trims and the normal bank…

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

Yes, that's what I'm thinking also and I am pretty sure I have it solved. I tried to edit my post earlier but it doesn't appear that it went through but here's where I'm at now. I was getting ready to do a mechanical flow test on the injectors using a guage and injector tester when I noticed the colored bands on all 4 left bank injectors was thin and orange and right bank was tan and roughly…

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Albert Owner/Technician
Towanda, Pennsylvania
Albert Default
 

Sounds like you found your issue. great post

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Tamiyal Educator
Miami, Florida
Tamiyal Default
 

Do you have the data or screenshots of the initial injector flow test results using the scan tool? I would like to compare the Bank 1 and Bank 2 data.

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

Sorry but I didn't save that data as it was of no use. Using the injector flow test on the snap on scanner indicated all injectors had the same ms reading I don't remember off the top of my head the number because as soon as I saw all 8 the same I moved on . I didn't believe the results that's why I was setting up to do a mechanical test with a guage and an OTC injector tester when I noticed the…

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Joel Diagnostician
Freetown, Massachusetts
Joel Default
 

Looking at the STFT it looks like Bank1 was going rich under load/rpm (-19 fuel trim) while Bank 2 (+43). It wasn't an even split in opposite directions, but thought is may have been a clue. The VE is also a bit low for this engine. The graphed data makes it much easier to see data values and trends. Before the data mentioned it was most likely a man made issue and even mentioned to check…

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Default
 

Thanks for the input Joel I learned a little about reading data on this one so it wasn't a total loss for me

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Charlie Owner/Technician
Freetown, Massachusetts
Charlie Resolution
 

HELLO ALL. Just wanted to update this case. Swapped injectors from 1 bank to the other and lean code followed injectors from bank 2. further inspection of injectors part # revealed that bank 2 injectors were from a 2004 f150 with a 5.4l engine. After swapping in new injectors reset KAM and road tested vehicle again checked fuel trims while driving and after road test and found fuel trims equal…

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Geoff Diagnostician
Lahaina, Hawaii
Geoff Default
 

Great! I've seen that on a used engine swap once too. Those bands really help once you know about them. Good job, thanks for sharing.

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