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I'm sorry to hear that you have had so much trouble getting your vehicle fixed, and are still having trouble. Unfortunatly, this will likely not be an easy fix. If you are having a dead miss on two cylinders, this is likely what is setting the O2 sensor faults. Under normal conditions, the sensors measure the amount of oxygen leftover after combustion. If there is too much oxygen, the PCM richens (adds fuel) the mixture. If too little, it leans (takes away fuel) the mixture. Under a dead miss condition, along with unburned fuel, lots of extra oxygen is added to the exhaust as well. This results in low voltage from the O2 sensors signaling the PCM that the engine is running lean, so it adds fuel. So not only do the missing cylinders pump out unburned fuel, but as a result, cause the working cylinders to burn even more fuel.
The reason I say it most likely won't be an easy fix is because the early 4.7 liter engines had problems with the valve seats coming out of the head. It can cause the cam followers to pop out as well. Though it's possible that it's something as simple as spark plugs. A compression test should reveal whether or not the seats have dropped. Considering the condition, I would start with a compression test first and go from there. I seriously doubt that it is a programming issue. It may be a good idea to stick some new spark plugs in after doing the compression test. The other possibility is injectors, stuck or plugged. The way I usually verify this is moving ones from the non-firing cylinders to a known good and put the known good injector into the non firing cylinder. If the miss changes to the cylinder that was once working, you know that injector is bad. This test may also work with the spark plugs, if you want to check before just replacing them. But most likely, I would say your problem is internal and mechanical ( the dropped valve seats).
I hope this helps. If you have any further questions or need further information, feel free to ask. There is no need to accept until you are satisfied.
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