BN76

I have a 2005 F150 5.4 Lariat. Over the last 3-6 months I have noticed it losing power and shuttering when accelerating or going up hills. It has been continuously getting worse. I also have been getting a rough idle lately. Using a scan tool, I get the following error codes:


Bank 1 Lean (consistently get this)
Catalyst System Efficiency below Threshold (Bank 1, consistently)


I also get cylinder 1 misfiring first, then sometimes cylinders 1 and 2, then 1, 2, and 3 along with random cylinder misfire.


Using the scan tool I can also see that both oxygen sensors on bank 1 bounce up and down a lot. The bank 2 upstream O2 sensor looks similar, while the bank 2 downstream O2 sensor is stable at ~0.7. The short term fuel trim on bank one will spike up briefly while idling to 10-15%, and when the vehicle shutters on acceleration or going uphill the bank 1 short term fuel trim will spike up above 25%.


Before getting the scan tool, I suspected the FPDM, but now I see that the fuel rail pressure is consistently at about 40 psi.


The issues are always on bank 1. Are there any places where a vacuum leak would only affect bank 1? Could the fuel line be plugged somewhere between the pressure sensor and the bank 1 injectors?


Any ideas on what to check next would be greatly appreciated. A diagram showing where all of the vacuum lines come out of the manifold would also be helpful.


Thanks in advance.

F150Torqued

[MENTION=205253]BN76[/MENTION];


You've provied Very helpful diagnostics information. Interestingly - the PCM says Bank 1 lean - which is confirmed by both Bank 1 O2 sensors cycling - instead of the downstream sensor settling down like you describe your Bank 2 downstream sensor. BUT you report fuel Trim on Bank 1 is +. That's BACKWARDS (even though Long Term Fuel Trim is generally more meaningful) - The PCM is lengthing injector pusle width in an effort to richen the mixture - but the O2 Sensor says it ain't working. Electrical causes of misfires should result in negative going Fuel Trims because of unburned fuel getting to the O2 sensor causing an over rich condition. (That is unless the misfire is too severe/frequent, the PCM will shut the injector OFF to protect the CAT).


Possibility #1 - One or more of the 4 bank 1 injectors is plugged / restricted? Thus increasing fuel trim to that bank trying to get the O2 sensor happy. Running injector cleaner through MIGHT help, though it seldom does. Inspect spark plug tips for rich / lean indications before replacing any expensive injectors.



Yes: Possibility #2 But probably only an Intake Manifold gasket leak on a bank 1 intake port(s), or perhaps a cracked plastic manifold on a passanger side runner. To eliminate this possibility, Spray carberator cleaner or starting fluid (after getting your fire extinguisher ready) around / under the IM while monitoring Short Term Fuel Trim and/or O2 sensor signals. Two major vacuum ports are located on the bottom rear of the IM between the IM and firewall (1 for Brake Booster and 1 for Fuel Rail Pressure Regulator). Spray between the engine and the Firewall. A very good picture is here: http://www.ford-trucks.com/forums/10...ml#post9929436

Possibility #3 Perhaps - an exhaust leak allowing extra oxygen in the exhaust stream? A stethoscope or spraying carb cleaner around there while monitoring O2 sensor reaction might help eliminate that.

I Agree with you - I don't think the FDPM has anything to do with your symptoms, although a common problem. I believe it's more likely an intermittent total won't run problem.


I have no diagram, but there are minimal vacuum connections (two) on top, plus the major ones shown on the above link. I believe a leak in any of hose would effect BOTH BANKS.

Hope this helps. Good luck

primalurges

You could have one or more weak coils and or bad spark plugs on that side that are not igniting fuel causing PcM to think you need more fuel. You may have an exhaust leak before O2 sensor or a cracked intake manifold. I would start by swapping all coils from one bank into the other to see if the lean condition changes side. If it does its a coil or two of it doesn't Id try changing the spark plugs. If no luck Id work my way to exhaust manifold next
And intake last.

MGD

Beautiful post - the best that I have read in quite some time!

Ol'Blue72

I too have experienced the same lack of power. I have replaced my FPDM but it was because the pump wasnt pumping fuel to injectors, and it felt like a hard transmission slip. It is a hard jolt. Kinda scary actually. I have also changed plugs...TWICE. Throttle position sensor, All eight COP's, and bought headers to replace the warped factory manifolds(which I havent gotten on yet. I am scared to replace the rail or any of the injectors, but i cant continually keep changing parts. I have an older truck that needs the parts and attention more. LOL I have run a bottle of gumout professional fuel system cleaner and am gonna try another after this tank empties.

techrep

iTrader: (1)

you mean besides one of your's...lol

Mod (Ret.)

Yuuuuup. As long as we have our southern draw glasses on! Kudos to F150Torqued for the fine writeup.

techrep

iTrader: (1)

That's correct... :}

bourgeois1269

F150Torqued^^^^^^ sounds like someone has been in the field for quite some time. Good to know and very helpful advice for anyone that encounters this experience in the future.

MGD

Thankee fellers ... comin' from you two fine folks, thet thar's a mighty fine compliment! Ol' Bubber's humbled.

Cheers!
Regards;