Hi, I'm Jen, new to the forum (well this is the 1st time posting, but I've been stalking for a long time) I'm needing some advice or suggestions. I'm going to try to keep this as short as possible but doubtful I can do that.
I have a 2000 f150, 5.4, triton v8 with 280,000 miles approx. I've owned it for almost 5 years and the only real problem I've had with it up until now was the starter solenoid, which has been taken care of.
The truck has issues with accelerating, especially on hills and the longer I drive it, the worse it gets to where I can hardly move at all. I can be on the highway with the cruise set at 75, get to a hill and it loses power. The rpms will go up real high but I'll be losing speed at the same time until I'm over the hill and then it would act fine, until another hill. When I start the truck, it'll idle ok at first and I can Rev it up without any problems for the first minute after starting it but can usually only Rev it once or twice before it loses power, starts to sputter and will backfire if I keep trying to give it gas (I say backfire but I'm not sure if that's what it is because it sounds like it's coming from the engine compartment and sounds like a popping noise) when I'm driving and it starts to bog down, I can put it in park, turn it off for a second and when I restart it, it'll run a bit better for a little ways. It kinda sounds like it's congested when it starts to bog down but it seems like something resets itself for a minute when I restart the truck since it works better for a moment. When I first got the truck the obd codes it had on it were system too lean, bank 1 & 2. Someone told me that it was a vacuum leak so I replaced some questionable hoses but the codes came back. I tried spraying starter fluid around hoses to see if it reved up but it never did. Even with those codes, it ran perfectly until a couple months ago. I was told it was probably an o2 sensor and the person started to replace the upstream sensors, with some "brand new ones that would work for my truck" but turns out they had no idea what they were doing, because they started trying to remove the downstream ones instead, rounded the nut on the o2 sensor to where there is no way to get it out, at least that I'm capable of doing and the o2 sensors he had were not compatible with my truck (he's been fired and banned from touching my truck) so I ordered 4 brand new o2 sensors and put 3 of the 4 on there myself after watching YouTube videos and reading posts on this forum. I still have 1 empty spot where he messed up the drivers side downstream sensor, so I'm not sure if that could be causing all the problems or not. I replaced my air filter a year ago, but live on a dirt road. I took the filter out and used an air compressor to blow the dirt out of it. It wasn't too terribly dirty but that didn't help either. I checked the fuel filter on the frame and gas was flowing through there just fine. I can hear the fuel pump kick on when I turn the key to the on position. I had misfire codes for 5 and 7 and replaced the spark plugs there. The coil on 7 was kind of messed up so I replaced it too. I'm pretty sure if I ever need to replace the 7th one again I'll just catch the truck on fire instead. The only codes it has now are the system too lean bank 1 and 2, and the downstream o2 sensor that is missing. I still have the catalytic converters and they've never been messed with. I've tried sea foam and other additives in hopes it would help. My thoughts now is that maybe there's a clogged fuel injector but I'm not sure where to start on that. I would just replace them but oreillys says that they're $88 a piece and I feel like my truck really isn't worth spending that much money on 1 thing lol. Any and all ideas and suggestions would be greatly appreciated. This is my first time working on a vehicle myself and I really don't know much about mechanical stuff, so bear with me, I'm trying! (I do know how to use Google and YouTube though) If u made it to the end, thank u for taking the time to read this.

 

Since it is affecting both banks it is likely related to something common to both sides like the MAF (mass air flow sensor)

All the sputtering and backfiring needs to be diagnosed. Likely cause is a fuel problem. A fuel pressure check is warranted. Also check the fuel pressure regulator.

You need to get that fixed . The computer is likely trying to compensate for the missing sensor data and it could add to your issues.

 

I would tend to lean towards the PCV hose behind the i take facing the firewall.

​​​​​​​Beyond that, at 280,000 miles, I question the health of the engine in general.

 

I am concerned about your fuel and whether the processor is bringing the timing down because of spark knock
Next time you go up a hill and are barely making it, turn it off and restart it.
That will reset the timing, and it will have its power back if fuel was the problem
Check the fuel trims and report back