I have a 2000 f150 with a 4.2lv6 its getting 7 mpg I have changes. Plugs wires o2 and filters used good gas in it runs good. What's wrong with it
Does your truck use two spark plugs per cylinder? We had a 2000 Ranger with that emissions set-up, at work, and it got terrible gas mileage!
No just six three on each side changed everything had to cut the cats out changed coil pack plugs wires plugs fuel filter are filter o2 sensors both upper and lower strem no cats just flex pipe for now I have a vacuim hose from the intake to the cpvc valve that was calpesd.fixed it still did not change throwing black smoke running rich
Perform a vacuum test on your fuel pressure regulator on the fuel rail. Or, check your fuel pressure and see if the fuel pressure with engine off has a minimum of 50 to 60 PSI. If so, then start the engine and note the fuel pressure of around 30 to 50 psi. If the pressure remains at 60 then the fuel pressure regulator could have a hole in the rubber diaphragm which you can't replace. Just buy a new regulator.