I have a 06 F150, 4.6L with 125k mi. Over the past 6 months I have had repeated codes showing up indicating multiple random misfires and lean banks. I have changed coil placks, plugs, boots and had the intake gasket changed. This will normally fix the problem for a week or two and then it reappears and the truck runs rough and mpg drops off. Was told that it might be a wiring harness that is chafing but can't find any info to point me toward which harness. Any insight would be appreciated.

 

Hello Bob Towell
I would like to know if this happens to you around 1200 RPM if you have a tachometer unload or going from coasting to slight acceleration, say somewhere between 45-60 MPH?

 

No. The misfire/sluggish/rough running happens at all RPMs, speeds and conditions. Even at idle.

 

Have you look at the injectors ? and what brand parts are you using ? If the engine has been mis-firing for some time.. it may have clogged your Cats too.

 

OK by cat's do you mean "CAT - Catalytic Converter" and no did not check the Catalytic Converter as the is no smell and the tail pipe has flow and puts out water like it should. I have not seen anything alarming like a wight or blue cloud. as far as the COP is has been from advance auto but is now Motorcraft on #1, Replaced the #1 injector with a BWD Fuel Injector (best review) as it good for a weak and then back to the same 301 ans 312 codes. it is always #1 for years now. my next step is the injector electrical connector, seems the plastic clips are now week, perhaps from heat and old age.