When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 2012 Ford e150 4.6 liter. The van is running good but bad on fuel mileage. My LTF for both banks are at a steady -21% Stf for both banks jump between 0% and -8%. @2500rpms LTF stays the same at -21% and STF goes down and jump between -14% and -10% I cleaned the MAF sensor and readings are good. I also changed out air filter. I've changed the fuel pump just before the testing. My throttle position sensor is 15% at idle and 76% wide open. O2 sensor's readings seemed good, and also dont think its a injector leak because both banks are under the same rich condition. What could be possible problem with this issue?
Possible high fuel pressure. Does the oil smell of gas? If it did that would suggest a leaking injector or raw fuel being sucked into the motor some other way... often via the evap system or a broken FPR diaphram.
if you have a fuel pressure regulator, take a look at it, if its vacuum controlled you could have excessively low or high vacuum. If electronic, it could be a bad electrical connection, maybe it's a fuel flow sensor that went bad, try to look at things that are related to the fuel system and emissions system.
Possible high fuel pressure. Does the oil smell of gas? If it did that would suggest a leaking injector or raw fuel being sucked into the motor some other way... often via the evap system or a broken FPR diaphram.
wouldn't I get a code if it was evap system? No codes are pulling up.What's a FPR diaphragm? I will smell the oil and see if that would be the issue. If injector leak, it will have to be more than one correct? Because both banks being rich
Are your fuel trim readings freeze frame or snap shot readings or are they graphed in real time? Apart from the MAF and O2 sensors I don't know else could account for such high negative LTFT readings. I don't like spending your money but if any of those are even close to their lowest acceptable operating ranges I would suggest considering replacing them.
Overall you certainly have a fuel supply or emissions issue. Not for nothing but I have a somewhat distant similar issue where my STFT's are "normal"--show good switching-----but the LTFT's are about -3% when monitored during extended drive times. I also get a DTC saying my catalytic converters are occasionally running below a threshold that pops up after times of extending idling. (When I cancel the DTC it doesn't pop right back up so at this point I'm not overly concern about it.)
Please keep us up to date on what you find---could be helpful to others in the future.
I'm not in my shop to check your year, but have worked on similar problems the past couple of months of various vehicles -- I don't remember (exactly) the TPS readings for your year but I've normally set / test these at 12-13% rotational (.9v off the sensor) at closed throttle -- these TPS normally throw P0120-P0125s if bad, but CAN affect fuel ratios and not be within the EEC (PCM) overall fuel monitoring LT/ST Fuel Trim P-codethresholds (triggers )............
The fact both banks are affected as your trims are showing is helpful diagnostically....after your rule out fuel in oil (common with mechanically worn out older 4.6L and cousin 5.4L and sister-cousin 6.8L) I'd revisit the TPS and re-do a cleaning on the MAF, throttle body, etc...............flaky EVAP (leaks) === intermittents ==== may also be a contributing factor, quality of gas too.
Ongoing worn out engine internals would also affect the O2 readings........(very common in high mileage (worn) vehicles)
Update: tested out purge valve for evap and there's no leaks. It opens and close like suppose to. I also changed out throttle body with sensor. Percentage dropped to 9.8% at closed but fuel trims are at the same rich condition. No fuel smell in the oil. I'm stuck now. What should I test next?
Hey guys. Is there anything I can do for a old van with 497000 miles on its factory motor and trans. Aside from the obvious rebuild in need. It runs okay. The oil does smell like gas, seems to have an occasional stumble and a surge issue. Lyft 20.3 on both banks 3.0 and 4.6 stft. P0405 P10172 ect..
new plugs , coils, fpr, maf,throttle body and tps, new purge valve vent valve, branused dpf, cleaned the injectors, intake manifold gasket,new rad, new bat and terminals,
air filter, new oil filter housing gasket “that was beyond hard” I know in polishing a turd
Redrum,
The evap system will not set a code if the canister is contaminated with fuel
Your rich condition can be for many reasons (MAF, EVAP, Leaking injectors, Faulty O2 sensors) To name a few
You said the O2 sensors seemed good ? Need to know if they are switching like they are supposed to or if they are stuck above .5v
You have not been overfilling the fuel tank and polluting the carbon canister right?
Most likely you have leaking fuel injectors combined with slow switching or inoperative O2 sensors
More testing is needed
The EGR code? Ford 4.6's plug up the port in the intake manifold throttle body adapter (upper plenum)
It has a new maf, took the injectors out and cleaned them and replaced the ones that seemed sticky. New fpr reading 40 psi. New vent valve new purge valve, I have the canister disconnect because of the PO over filling issue. It’s been unhooked for a while now. But I used something similar to take it’s place. I just put all new o2. New data
Bench test the injectors and make sure none leak
Have the dealer painstakingly put it to the tests
They have better testing options now but back in the day at the dealer we would have put your van on the SBDS machine and painstakingly hooked up the machines injector harness
That gave us cylinder balance info and had an injector leak down test as part of it
You can do this yourself on the bench. Not easy though
I have a spare rail that I use
I pressurize the rail with fuel injector cleaner and apply voltage to the injectors
You can see if any drizzle and you can inspect the spray pattern
Next time you have them out you can find a rail at the wrecking yard cheap and do that test if you 2 are still stumped
