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I changed the plugs and coils on my ford 4.6. I still have misfire and high fuel consumption.?
2 Answers
- 1wbrockstar2004Lv 66 years ago
I would check for vacuum leaks,injector and injector harnesses,egr valve cleanliness and function and clean the maf sensor with maf cleaner or electrical cleaner.Buildup of grime on the heated wires will cause the maf sensor to malfunction. You can use carb cleaner or a small propane torch with the valve open,to check for vacuum leaks.Start the engine and let it idle,spray carb cleaner directly on or run the torch tip directly alongside every gasket,vacuum hose,vacuum fitting and vacuum operated component. If the engine suddenly idles up or stalls,the area you just sprayed is where the leak exists.To check the injectors,let the engine idle,disconnect a injector wiring harness,slide a safety pin into one of its terminals,attach a test light clip to that pin then probe the other harness terminal. Is the light flashing,if so the injector harness is ok.If not,test another harness and if the result is also no flashing,the injector power feed wire is open/shorted.
Source(s): If the light is flashing,reconnect the harness,hold a screwdriver tip against the injector body and hold your ear to the screwdriver handle,you should hear a repetitive clicking noise.If yes,the injector is ok.If not,the injector is bad.A dirty injector can also cause a misfire,but you would have to remove it in order to inspect it for that condition. A rebuild kit is sometimes available that includes a new pintle cap,orings and filter screens.Search the site below for egr valve testing.Its a great technical forum for Mustangs and other Fords.The 4.6 is also well known for developing a misfire due to leaking/deteriorated pcv hoses at the valve or intake and also the egr valve vacuum hose.Make sure these hoses are intact because thats an easy cause for a vacuum leak on these engines.Make sure the correct vacuum hose is attached to the egr valve too because it is sometimes crossed up with a vacuum hose that is suppose to connect to a different component. If you pull codes and get any lean bank 1 or 2 codes,the pcv valve or egr valve hose is almost always to blame,unless the o2 sensors are malfunctioning. http://sbftech.com/ - 6 years ago
could be one the Distributor, timing, injectors, or a dead cylinder (unlikely). Change the cap and rotor first since its cheap and easy.