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#4812273 - 07/12/18 01:22 PM 2009 F150 Fuel Trim Help
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
Got my 5.4 3V replaced a couple months back due to a dropped valve.

Since I got it back, Iíve had a rough idle, a little shutter in drive when I let off the brake and then it runs great.

Iíve used numerous code readers and scanner and there are no active codes. Just left the engine builder and he is thinking I have a clogged or leaking hector. After plotting the short term fuel trims there is a strange difference between the two.

On the same time scale the bank one trim bounces up and down around 2-3x more then bank 2. Bank 2 is consistent with a couple higher spots when the a/c compressor kicks on and off. Bank one is a jagged up and down with essentially no smooth section.

Iíll work on sharing a picture of what I plotted but what would make the short term fuel trim on one bank bounce 2-3x more then the other bank. I have all new coils and the engine runs great at higher RPM. Is it time for new fuel injectors? There are 166k on the truck.
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812275 - 07/12/18 01:26 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston


Edited by PReal (07/12/18 01:26 PM)
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812301 - 07/12/18 02:00 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812334 - 07/12/18 02:47 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
Jethro_Bob Offline


Registered: 06/26/18
Posts: 1
Loc: AR
Have you compared front o2 sensor readings for the 2 banks? If bank one isn't jumping around with the fuel trim, it could be in the process of failing and sending incorrect data to the pcm.

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#4812336 - 07/12/18 02:49 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
O2 fuel trims were bouncing around consistant with the trim on both banks.
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812412 - 07/12/18 03:57 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
Trav Offline


Registered: 11/20/06
Posts: 19314
Loc: MA, Mittelfranken.de
Injectors are always a possibility but I would look for a vacuum leak, possibly PCV system.
_________________________
ASE L1, Master. Deutsch Meisterbrief.

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#4812426 - 07/12/18 04:13 PM Re: 2009 F150 Fuel Trim Help [Re: Trav]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
Wouldnít a vacuum leak effect both banks? Itís only one side of the engine to me whose is what is so strange.

I donít think the pcv is serviceable on my truck.
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812453 - 07/12/18 04:55 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
cb_13 Offline


Registered: 07/24/11
Posts: 930
Loc: Missouri
Originally Posted By: PReal
Wouldnít a vacuum leak effect both banks? Itís only one side of the engine to me whose is what is so strange.

I donít think the pcv is serviceable on my truck.


PCv is a metered orifice in the valve cover on the 5.4 3v. A vacuum leak from an intake gasket could affect only one cylinder bank.

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#4812458 - 07/12/18 04:57 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
How would I diagnose a vacuum leak on the intake manifold? Smoke test?
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812470 - 07/12/18 05:04 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
Also, even with a vacuum leak on one side, wouldnít I get a consistent fuel trim but just a richer percentage to compensate for the additional air?
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812492 - 07/12/18 05:37 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
cb_13 Offline


Registered: 07/24/11
Posts: 930
Loc: Missouri
Originally Posted By: PReal
Also, even with a vacuum leak on one side, wouldnít I get a consistent fuel trim but just a richer percentage to compensate for the additional air?


Likely, although I'm not familiar with monitoring fuel trims on a snap on scanner I'm only familiar with IDS. So that readout looks Greek to me.

Easiest way to rule out a vacuum leak is if the fuel trims return to around 0 when opening up the throttle. As the engine will overcome the vacuum leak with
the throttle opened. Smoke testing the intake or spraying brake cleaner around the plenum will also find it.

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#4812494 - 07/12/18 05:43 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
PReal Offline


Registered: 02/09/14
Posts: 188
Loc: Houston
Iíve stayed the plenum with brake cleaner and didnít see any rise in rpm.

That dang fuel trim is crazy. I canít comprehend anything that wouldíve the fuel adjust 2-3x more often then the other side except a partially bad injector. Since the O2 reads all 4 on that bank, one cylinder rich/lean would drive it to more adjustment. If all cylinders were lean/rush id get a code due to multiple misfires.
_________________________
2009 F150 5.4
2008 Yukon 5.3
1996 F150 4.9 M5OD
1966 Ranchero 289 T5
1965 Mustang 306 T5

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#4812527 - 07/12/18 06:25 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
SHOZ Offline


Registered: 06/28/03
Posts: 5809
Loc: Illinois
What do the primary O2 voltages look like between the two banks?
_________________________
2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual

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#4812532 - 07/12/18 06:35 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
Trav Offline


Registered: 11/20/06
Posts: 19314
Loc: MA, Mittelfranken.de
Fuel trims will be different depending on if its ported or manifold vacuum. Manifold vacuum will be higher at idle and low rpm causing fuel to be added in that range, ported vacuum will increase with rpm and have the the opposite effect on trims.

Yes a vacuum leak can effect one bang more than the other depending on the location of the leak if there is in fact one.
An intake leak near 2 adjacent ports for example with drive the mixture lean on those 2 only but because you have only one wide band on each bank it will adjust the trim for the whole bank they are on.

What are the exact readings for bank 1 and bank 2? For example bank 1 +10 and fluctuating and bank 2 +3 more stable.
Spraying brake fluid all over isn't the best way, the reading may be too short lived, try (unlit) propane with a nozzle and extension hose and watch the trims for a few seconds as you move along the manifold, plenum, hoses and connections, keep the flow wide open or almost at the valve.

https://www.homedepot.com/p/Bernzomatic-WH0159-Universal-Torch-Extension-Hose-361542/202539579
_________________________
ASE L1, Master. Deutsch Meisterbrief.

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#4812547 - 07/12/18 06:50 PM Re: 2009 F150 Fuel Trim Help [Re: PReal]
WobblyElvis Offline


Registered: 09/23/14
Posts: 1386
Loc: Toronto Canada
The Power Brake booster? Just a thought.

The ScannerDanner forum is just the place for this kind of question. I suggest if the answer doesn't present itself here, you give them a try. Put together all the info you have a explain the problem as clearly as you can.
https://www.scannerdanner.com/forum/post-your-repair-questions-here.html

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