Boy o boy I NEVER get that lucky! Congrats, I hope that is the end of it for you.

 

Excess unmetered air - will do it every time!

That tube is the PCV inlet.

 

while FORD did not find it necessary to put a clamp on them ...i found a simple ziptie works well...without deforming the plastic tit

 

Well, my luck ran out. The 171/174 codes came back .....

Made a smoke generator and ran a smoke test to find out where a vacuum leak might be, but could not detect any leaks. This seemed to be consistent with the freeze frame data that showed the problem only occurs under load, pointing to a fuel side issue. So, I did the obvious and replaced the fuel filter, but the codes came back after about 30 miles of driving.

The engine is still running fine which made me think the fuel system is working properly. But since I can't find anything specific, I gave in and took the truck to the dealer for diagnosis. Their cost for diagnosis was the same as other shops.

Their findings confirmed that there is no vacuum leak. But, the fuel pressure was only 30psi and the spec is 35psi. Their recommendations were to replace the fuel filter then the fuel pump.

I just did the filter, so I am looking at a new fuel pump, UGH! The dealership quoted over $1000 to do the job.

Now I have to decide if this is something I can tackle by myself. I've seen the videos of removing the bed. That seems like the way to go, just not sure if I can do it. I'll call around for other quotes too.

 

Maybe it's just the fuel pressure regulator?

 

They did not indicate any test results for the regulator. I presumed low pressure in the system is low everywhere.

 

Get a fuel pressure gauge - most parts stores have them in their loaner tools. See what the pressure is at idle and 2000 rpm. Then pull the vacuum hose off the FPR and repeat the tests. By the way, spec is 28 to 40, when you pull the hose it should rise at least 5 psi. If it doesn't rise, you probably need a fuel pump. If it does rise, I'd suspect the FPR.

 

Just drop the tank.

 

I did find some similar specs saying the range was 30 to 40 psi. I suspect the dealership just picked the middle value as the recommended number. Since I am at the bottom of the range, but not quite out of it, is likely why it is still running ok.

I will just replace the regulator. The dealership said they recommend changing the regulator and filter with the fuel pump anyway. Given the age and mileage of the vehicle, a new regulator is likely warranted, like the pcv valve. I will replace it and see if that solves my problem. If not, I'm one step closer to finishing the job.

The first problem is I have to find it. Right now I don't see it. Looking at the parts photos on RockAuto, it appears to be some type of push-in device with an inlet/outlet tube on the ends.


From what I've researched on youtube, the folks who have done this say removing the bed is much easier. I only go by those comments. I'm still researching

 

It's on the fuel rail. The end with the O-ring plugs into the rail, the other end has a vacuum line on it.

 

Well.... that was easier said than done.

I found it with the help of an inspection camera with an end-lighted cable lens.

For those who are wondering, it is at the back of the engine, on the passenger side, buried deep behind a ton of interference. A c-clip has to be removed and reinstalled to remove/replace the unit. Access is going to require serious stuff removal. Getting a c-clip pliers in there will be a challenge. I checked my Chilton manual, there's nothing in there about removing the regulator. Not finding anything on youtube for the 4.2 L engine

Anybody know of any tips, good tutorials, how-to videos for getting at/removing the regulator ?

 

Well I knuckled under to the pressure, ( pun intended) and got a fuel pressure test kit on loan. I checked the pressure key-on/engine-off and found that the pressure initially goes to about 40 psi but then bleeds off steadily and rather quickly. Not sure if this is because of the fuel system or the fuel testing gauge. I can't get a completely dry connection with these fittings.

With the engine on: it stays steady at 30 psi. Snapping the throttle, it goes up about 5-10 psi then quickly goes right back to 30 psi. Disconnecting the vacuum line on the FPR, causes the fuel pressure to go up about 10 psi.

Not sure how to interpret all this. Still researching. May need to find a way to pinch off the return line, if I can identify it, and a spot to do it without damage.

 

With the key off, remove the vacuum line from the FPR, see if any fuel drips out. If it does, replace the FPR.

 

Your last checks show little to no issues except the pump is not holding pressure very long after shut down. That is not a big issue but needs to be remembered for the future as it's getting close.
.
171/174 resetting after about 30 miles indicates an air leak the OX sensors are detecting both banks requardless of your testing not showing any leaks.
The sensors are a lot more sensitive that your testing as they must detect the Ox content "after every cylinder firing" at all RPM and report that back to the PCM for correction to the "next cylinder" in the fire order to keep the A/F ratio within limits..
That's pretty fast action. (The PCM clock frequency is very fast to do this ).
If Ox sensors detect excess air, that peg counts the long term fuel tables to the rich side trying to correct from the air leak effect.
With this action you won't see any difference in engine running but reduced fuel mileage if you were to notice over a few tanks full check.
The long term fuel tables are ZERO centered meaning they can move either way. (a matrix) array.
Moving to a plus % = rich, moving to a negative % = Lean.
The rich and lean has separate codes assigned. 171/174 for a + shift and 172/175 for a neg.% shift.
Notice the codes say 171/174 lean, 172/175 says rich. This is describing the conditions in the intake tract the Ox sensors are responding to. Often missed by those who are not familiar with the way the descriptions are written.
This is why feedback sensors are almost never are the issue but monitor the operating and control conditions.
The sensors are the only way the system has to detect a 'system' fault and not the fault themselves unless reported with different codes.
Some sensors like the Ox sensors are looked at by other parts of the program and have separate specific fault codes assigned you are not seeing.

 

I did do that before all the test work ( to make sure i could reach it) and no fuel dripped out. The vacuum connector was dry. I'll double check it after the next test.

Thanks for the reply. I do appreciate all input. But everything in this long, long journey is now pointing to a fuel side problem. Codes appearing only under load, negative smoke test results, dealership confirmation of no vacuum leaks, low-fuel pressure at idle, ( measured at the dealership and by myself ), and no fuel pressure hold, all point to a fuel-side problem. Dealership already declared it a pump problem. It may not be a broken pump but a just a clogged strainer. Repair work will be the same.

The only remaining test is to pinch off the return line and measure fuel pressure change. This should distinguish between a regulator/pump problem. This will just be confirmation for double checking.

I just need to find a location to do this last test.