Hey I have a 2005 Ford v8 5.4L.. Recently my check engine came on, and when I was coming home that day i could barely make it up the hill at 50mph (pedal to the floor). So i parked it and the next day the issue remained. Symptoms are reduced engine power, engine is hesitant (as in my foots on the floor), and the engine makes a clunking noise trying to go uphill and stops moving. It starts up perfectly and idles under 1000rpm and doesn't stall. So i've ruled out spark plugs being bad, and i've been told maybe its bad gas (lean gas). So i've tried putting in addictives such as water remover and octane booster to help the gas but the issue remained. I then went and cleaned my MAF sensor attached to my K&N filter and that didn't help. The truck still runs but something about going uphill isn't sitting well, i feel like its a fuel issue or possibly i need to clean my fuel injectors ? I would bring it to the shop but i can't afford the repairs for a couple weeks. Any ideas or opinons would be appreciated, thanks.
I have been having the same problem on mine and have been told that the fuel filter could be bad or possibly the O2 sensor is going out. Please let me know if you find one of these to help. I am in the same situation with getting it fixed.
First things first, check what the codes are. Chances are it will be lean on both banks. Check your fuel pressure at the fuel rail and also before the fuel filter. You can do both of those for free at your local parts store. They might not even make you pay for the pressure tester if you use it in the parking lot.
If it doesn't do it on a cold start (sitting for two hours or more), it could be an O2 sensor. When the PCM is running in open loop, it will command fuel based on other sensors. When it goes closed loop after they warm up, the O2 sensor essentially controls your fuel.